a speech by Carlo Buckhardt

Abstract

In order to overcome existing restraints in the in-service behaviour of currently available additive manufacturing (AM) materials’ sets, an advanced production method for high performance technology metals was developed on the basis of a modified vat polymerisation-based (VP) printing for metal powders. The new lithography-based metal manufacturing (LMM) process is able to photoharden highly filled innovative metal-photopolymeric binder.
After debinding and sintering, the fully dense metal AM parts will provide various advantages such as superior properties with respect to cracks or internal stress when compared to laser-based powder bed fusion (L-PBF) AM parts. LMM is suitable to build very detailed, complex structures with a minimum of after-treatments without need for support structures, exhibiting superior surface quality, having less demanding requests with respect to powder particle size/morphology and allowing effective re-use of the feedstock materials.
In the paper, the LMM process will be explained in detail, its suitability for the production of jewellery and watch pieces will be demonstrated for stainless steel type materials and titanium alloys on various samples, an outlook for precious metal powders will be given

Pforzheim University

• founded 1899
• one of the biggest Universities for Applied Sciences in Germany (~6.000 students)
• threefaculties:
  Business, Economics & Law
  Engineering
  Design
• 29 Bachelor-and 17 Master-Courses
• one of 7 fully certified universities in Germany

Institute for Precious and Technology Metals

Partner oftheregional precision engineering industry

• contract research, serial inspections, damage analyses, expert opinions, production optimisations, etc.
• fully equipped materials lab; incl. 2 SEM, FIB, EDX/XRD, Laserscan, DTA, mechanical testing, corrosionetc. (DAkkSakkredited)
  National and international research partner
• recycling of rare earth metals/permanent magnets
• additive manufacturing of metals
  Head: Prof. Dr.Carlo Burkhardt
• 4 national projects, 3 international multilateral (EU) projects (>30 M€ overall budget)

LMM Additive Manufacturing

Lithography-based Metal Manufacturing

• basedon theVat-PolymerizationPrinciple
• verygoodsurfacecharacteristics
• verygoodgeometricalprecision
• nothermal distortions
• materials: stainlesssteel, toolsteel, titanium, […]
• suitable also for non-weldable materials
• printing speed: max. 16 cm³/h
• suitable for:
• smalland very small parts(<30g)
• smalltomoderate quantities

LMM-Process

How it works

LMM-Process

Sintering

LMM-Process

Shrinkage

LMM-Process

Precision

• finished part tolerances up to ±0.5% of nominal dimension possible
• stair-step effect due to layer-by-layer production

LMM-Process

Surfaces

LMM-Process

Some parts

MetShape GmbH

• Start-up and spin-off of Pforzheim University as of 01.04.2019
• funded by the program “Young Innovators” of the Ministry of Science, Research and the Arts Baden-Württemberg
• specialized in additive component manufacturing using the Lithography-based Metal Manufacturing process (LMM) and related development services
• main focus:
  • conducting feasibility studies for components and materials
  • small scale productions
  • installationof process chains for in-house production

a speech by Christopher W Corti

Abstract

Platinum has only been known to Europe since the 16^th century. This was impure platinum which is found as grains of native metal in alluvial deposits, often associated with native gold. Such grains are mainly platinum alloyed with the other 5 platinum group metals and were exploited by pre-Colombian Indians of Ecuador and Colombia in NW South America.

In more recent times, the popular use of platinum in jewellery dates from the early 20^th century, often as a basis for diamond (and other precious gemstone) jewellery.  Its use in jewellery was restricted in the Second World War as it was considered a strategic industrial metal with limited availability. Thus, early jewellery alloys tended to be based on the existing industrial alloys and comparatively little development of specific jewellery alloys was carried out.  Its acceptance as a hallmarkable jewellery metal came much later in 1975 when, with a wider availability of the metal, platinum was promoted as a high value jewellery metal and platinum jewellery started to grow in popularity, mainly at 950 and 900 fineness qualities. Since that time there has been alloy development specifically for jewellery application and tailored to the requirements of different manufacturing technologies.

This presentation reviews the evolution of platinum alloys over the last century against the challenges – physical and metallurgical – presented in developing improved alloys for jewellery application.

INTRODUCTION

Platinum has only been known to Europe since the 16^th century with rumours of the existence of a white metal, platina, in central and south America that cannot be melted¹. This was impure platinum which is found as grains of native metal in alluvial deposits, often associated with native gold. Such grains are mainly platinum alloyed with the other 5 platinum group metals (PGMs – palladium, rhodium, ruthenium, osmium and iridium) – and were exploited by pre-Colombian Indians of Ecuador and Colombia in NW South America. Analysis of ancient trinkets indicates that iron and copper were also present as impurities¹.

JEWELLERY ALLOYS: 1920s to 1999

In more recent times, the popular use of platinum in jewellery dates from the late 19^th– early 20^th century, often as a basis for diamond (and other precious gems) jewellery. Smith, in his book published in 1933², notes its use in jewellery at 99.5% fineness with small additions of alloying metals to harden it, including Ir, Rh, Ru, Au, Ag and Cu. He also notes that the platinum standard (in the UK) is 950 fineness and is finding general acceptance.  The term ‘platinum’ is deemed to include iridium.  He further notes that much of the platinum in use in jewellery is alloyed with copper to improve hardness and colour. The use of platinum in jewellery was restricted in the Second World War as it was considered a strategic industrial metal with limited availability, which led to the development of white gold alloys as an alternative for jewellery. Thus, early jewellery alloys tended to be based on the existing industrial alloys and comparatively little development of specific jewellery alloys was carried out. These tended to be 90-95% platinum alloyed with other PGMs, usually iridium. These alloys have high melting temperatures, making manufacturing of jewellery, particularly investment (lost wax) casting, difficult and challenging for the jeweller used to gold and silver.

A further issue had been the lack of accurate analysis techniques. All this meant that its acceptance as a hallmarkable jewellery metal in the UK came much later in 1975³.  From this time, with its now much wider availability, platinum was promoted by the platinum producers as a rare, high value jewellery metal and platinum jewellery grew in popularity, mainly at 950 and 900 fineness qualities, in Japan, Europe and the USA, although some growth in demand began earlier in Japan in the 1960s for historical reasons linked to the ban on the import of gold until 1973.  This marketing and growth led to some alloy development such as the platinum-cobalt alloy for investment casting⁴ and the use of gallium additions to produce heat treatable alloys with higher strength and hardness⁵ as Normandeau has reported⁶. For example, one European platinum producer lists only 4 alloys for jewellery application in their catalogue dating to the late 1980s, all at 950 fineness, namely platinum – copper, platinum – cobalt, platinum -ruthenium and platinum-gallium-indium. The copper alloy is listed as a general purpose alloy and the cobalt alloy is listed as suitable for investment casting. Another European producer lists only 3 alloys at 950 fineness:  Pt-5Cu, Pt-5Co/Ni and Pt-5Ru.

Huckle of Johnson Matthey reported on the development of platinum alloys to overcome production problems at the 1996 Santa Fe Symposium⁷. He noted that platinum and its alloys had some different characteristics compared to gold and silver, notably weight, hardness and thermal conductivity and that its alloys have a high density, as well as high melting points. Its high surface resistance leads to clogging (galling) and high wear of saw blades, files and machine tools. He notes that, in Japan, Pt-Pd alloys are in common use, particularly Pt-10%Pd, whereas in Europe Pt-5% Cu is preferred but that it is not a good casting alloy whereas for casting application Pt-5%Co is finding success. In the USA, he notes Pt-10%Ir is commonly in use as an all-purpose alloy and that Pt-5%Ru is used where a hard, good machining alloy is needed. He also notes Pt-5% Co is finding growing use for casting applications in the USA.

Maerz (Platinum Guild International) also reviewed platinum jewellery alloys at the 1999 Santa Fe Symposium⁸ and this built on the information provided by Huckle. It sums up the alloys widely available and their application in jewellery at that time with some comment on the new alloys being introduced, Table2.

In this context, Maerz and Huckle noted that it is important to recognise the different marking standards of various countries at that time. Maerz noted that European countries generally allowed only 950 fineness alloys, with some allowing no negative tolerance (Austria, Ireland, Sweden, Norway, Finland, United Kingdom and Switzerland), some allowing a small negative tolerance (Denmark, Portugal and Italy) and others allowing iridium content to be counted as platinum within the 950 standard (Belgium, France, Italy, Greece, Netherlands and Spain). In Germany, he noted that several fineness standards and alloys were allowed, Table 1.

In the USA, he noted that the standard for jewellery to be marked as platinum was 950 fineness but that the minimum amount of platinum allowed was 500 parts per thousand with the rest of the alloy comprising 950 parts per thousand total platinum group metals (PGMs) with a zero tolerance. He also notes that 950,900 and 850 fineness standards are allowed in Japan.

With regard to actual alloy compositions, he notes that each alloy is made for specific manufacturing functions. Some alloys are preferred for tubing or machining and others for casting, for example, and there are differences in preference in different countries. Table 2 lists the alloys in common (or growing) usage around the world with their function and countries of major use.  He also lists separately a number of alloys that are specific to Japan

Maerz’s list did not record the platinum-5% copper alloy (except its use in Japan) which has been mentioned above as an alloy commonly used in Europe. Maerz does note that, in the USA, the most common alloys in use are 950 platinum with 5% cobalt or ruthenium and 900 platinum – 10% iridium alloy. However, in an updated later version of this paper⁹, the Pt-5Cu alloy is included.

In his book published in 1984, Savitskii¹⁰ notes only two 950 fineness alloys are in use in the old USSR – Pt-5 Ir in Russia and Pt-4.5 Pd – 0.5 Ir in East Germany (GDR).

TECHNICAL ASPECTS OF ALLOYS: 1920s to 1999

From the list of alloys summarised in Table 2, it is evident that at 950 and 900 fineness qualities, there is a broad range of alloys available to the jeweller, each suited to various manufacturing techniques. All have a good white colour, although some may benefit from rhodium plating, e.g. Pt-10% Pd alloy, to give a brighter, whiter colour. The main differences lie in their hardness (or strength) and melting ranges.

Battaini has examined the microstructure of several platinum alloys¹¹ and notes many alloys are single phase, as one might expect from examination of their phase diagrams, particularly at 950 and 900 fineness qualities.  Some alloy systems, however, show large areas of miscibility gaps at low temperatures, for example Pt-Au and Pt-Cu systems and this raises the possibility of age-hardening alloys by heat treatment.  Platinum-5% gold is an example here, Fig 1(a), where an aged hardness of HV300 can be attained, leading to better scratch and wear resistance, but I have not observed its use in as-cast Pt-Au rings^12,13, suggesting it is a treatment not in common use. Platinum- cobalt, Fig 1(b), forms an ordered intermetallic compound, Pt₃Co, that could also enable some hardening at 950 fineness.  The use of gallium also allows age hardening, as is evident from the phase diagram, Fig 2, as well as lowering melting ranges and its use forms the basis of several heat treatable alloys as noted earlier.

Clearly, some alloys are quite soft (hardness lies in range HV50-100), some have a moderate hardness (HV100-150) and others are quite hard (HV 150 – 350), the higher values usually when in the age-hardened condition. In a recent study by the author of customer complaints^12,13, it has been noted that use of soft alloys is a significant factor in platinum jewellery becoming deformed in shape and badly scratched when worn by consumers, particularly in as-cast gem-set rings and wedding bands.

Work around the turn of the 21^st century and summarised in recent reviews^14,15 has demonstrated that microalloying of pure platinum and its alloys with small additions of calcium and/or rare earth metals such as cerium, samarium and gadolinium, typically up to about 0.3%, can increase hardness substantially but such micro-alloys do not appear to have been commercialised by the jewellery industry, probably because they are not easily cast or recyclable.

The melting point of pure platinum is 1769°C, considerably higher than gold (1064°C) and silver (961°C). Its alloys tend to have similarly high melting ranges, as shown in Table 3, although the gallium-containing alloys do have a significantly reduced melting range. Thus, melting and casting platinum alloys requires good furnace equipment capable of attaining melt temperatures some 100°C above the liquidus temperature of the alloy for investment casting. Induction melting is preferred. Melting by gas torch is not easy, although a propane or hydrogen-oxygen torch can be used by bench jewellers.  However, in general, working of platinum alloys is not a problem, although polishing requires skill and effort to obtain a good quality polish. Machining of platinum also requires skill to obtain a good smooth finish, requiring special tool materials and different tool geometries¹⁶, as platinum tends to gall (adhere) on the tool. The low thermal diffusivity of platinum alloys makes welding easier, particularly laser welding¹⁸ compared to gold and silver alloys.

The major manufacturing problem has been with investment casting.  The high melting and casting temperatures require use of special phosphate bonded investment mould materials¹⁹ and the poor melt fluidity requires use of centrifugal casting machines²⁰ to obtain good mould fill rather than the modern gravity machines commonly used for gold and silver. The new generation of tilt casting machines are also suitable. The chief problem with platinum casting is getting defect-free castings^7,20,21 and there have been several investigations on the relative merits of different alloys^4,22-24, looking particularly at surface quality, form-filling and gas and shrinkage porosity. The general findings from these studies show the Pt-5%Co alloy to be the best of current alloys but still not ideal.

JEWELLERY ALLOYS: 2000 to the Present

There have been several studies to develop improved platinum jewellery alloys in the last two decades. These have focussed on either stronger (harder) alloys or improved investment casting

alloys, although alloys suitable for additive manufacturing (3D printing) technology have also been of interest.

A] Stronger, harder alloys

The resistance of jewellery to abrasion and knocks – wear and scratch resistance – depends to a large extent on the hardness of the alloy. As noted earlier, a study of customer complaints showed platinum rings and wedding bands to be particularly prone to deformation of shape (misshapen) and to heavy wear (scratches and dents) during customer service (i.e. whilst being worn), when made in soft – moderately hard alloys. Hard alloys tend to be difficult to work in manufacture, especially to set gems in mounts, and so it is advantageous if an alloy is relatively soft whilst being manufactured into a piece of jewellery but can be subsequently hardened to improve its durability whilst being worn by the customer. This can be achieved by age hardening of suitable alloys after manufacture, a treatment involving the precipitation of a dense dispersion of fine particles of a second phase within the matrix grains.

For platinum, it has been noted that some current alloys are age-hardenable and alloys containing gallium have been developed specifically for this purpose. The first was the Pt-3% Ga-1.5% In alloy developed by Johnson Matthey⁵ and others have also followed such as the HTA alloy⁶ developed by Imperial Smelting and the ‘S’ alloys developed by S Kretchmer and discussed by Maerz⁸. Weisner, in a paper²⁵ presented in 1999, discusses heat treatable alloys and notes earlier work at Degussa, C Hafner, Johnson Matthey (Pt-Ga-In) and S Kretchmer (Pt-Ga-Pd) to develop heat treatable 950 platinum alloys. He notes that all are ternary alloys, many with melting ranges much lower than the conventional binary alloys, suggesting they all contain gallium and/or indium additions. Such alloys are useful for their spring properties in springs and clasps, for example.

Research²⁶ carried out at Mintek, South Africa in 2005 has examined potential platinum alloy systems with additions of 7% or less to identify suitable binary alloy systems that can be substantially age-hardened. Over 20 alloying metals were studied in the preliminary trials at levels of addition of 2 & 4 % and those showing promise were also studied at the 3% addition level. From this work, alloys with additions of Ti, Zr, Sn, Ga, Ge, Mg, In and V were studied in more depth. From this, along with consideration of other aspects, it was concluded that the best alloy was a Pt-2% Ti alloy which had as cast and annealed hardnesses sufficiently low to be easily worked and formed but with subsequent heat treatment, the hardness value could be increased by about HV90. Interestingly, there are parallels here with the development of 990Gold (Au-1%Ti) alloy²⁷. The Mintek work does not appear to have been further developed into a commercial alloy, possibly because it does not show much advantage over the existing commercial gallium-containing alloys.

More recently, a harder general purpose alloy, TruPlat™, has been introduced to the market in the USA by Hoover & Strong. It is a 950Pt-Ru-Ga alloy that is not age-hardenable. It has a higher work hardening rate compared to 950Pt-Ru, with an annealed hardness of HV180.

B] Improved casting alloys

The motivation here is to develop alloys less prone to casting defects, particularly casting porosity.  Use of alloys with lower melting ranges to inhibit mould reaction is desirable too. Work carried out by Fryé at Techform and Klotz and co-workers at FEM ^{23,24 28-30, 32} on platinum cast in shell and conventional moulds has focussed on which alloys are best in terms of casting porosity formation, form-filling and surface quality and establishing the mechanical properties of cast alloys. The use of computer simulation of the casting process has also assisted in optimising process parameters in casting. Fryé has also shown the benefits of a Hot Isostatic Pressing (HIP) treatment post casting in removing porosity from castings and improving mechanical properties. What is particularly noticeable is the growing number of new platinum casting alloys that feature in these studies.  This alloy development started a little earlier in 1997.

In a paper³⁴ presented at the 1997 Platinum Day symposium in New York, Lanam, Pozarnik and Volpe reported on a new investment casting alloy, 950 Pt-Cu-Co, developed at Engelhard, that combines the good properties of Pt-5Co and Pt-5Cu and reduces the issue of magnetism in Pt-Co alloy. It’s as-cast hardness is about HV119, somewhat lower than Pt-5Co. Porosity was still present and it had a tendency to form a surface oxide on heating.

Another alloy development was presented by Normandeau in 2000³⁵ in which he reported on a new 950 platinum Hard Casting Alloy (HCA) with an as-cast hardness of HV 160-170, much higher than Pt-5Co alloy. Little detail is given on the composition but the discussion in the paper points to it being a 950Pt-Ga-Ir alloy, since he provides data on the Ga:Ir ratio and it’s effect on hardness.

A further alloy development was presented by Grice & Cart in 2002³⁶ where the development of a 950 Pt-Au-X alloy, PlatOro™, is reported as an alternative to Pt-5Co. This has an as-cast hardness of HV125, a little softer than Pt-5Co alloy but is non-magnetic and has lower melting range of 1590° – 1629°C. This does not appear to be the Pt-Au-In alloy examined by Fryé & Klotz³⁰ and Maerz and Laag³³, Table 4, since the melting ranges and hardness values are different.  Grice has since reported³⁷ that the PlatOro™ alloy is actually a Pt-Au-Cu alloy but is no longer commercially produced.

Fryé and Fischer-Buehner in their study reported in 2011²⁴ recognised the inadequacies of the existing commercial casting alloys and widened their search to include 3 newer versions that contained undisclosed elements, which they designated as hard alloys (HV175 or greater). These are included in the table of alloys reported in Table 4. The platinum-cobalt- X hard alloy with unknown additions appeared to show some promise. The Pt-Ru-X alloy is now known to be the Pt-Ru-Ga alloy from Hoover & Strong³⁷ and the Pt-Co-X alloy is a Pt-Co-In alloy from Legor³⁸ and is harder and non-magnetic compared to Pt-Co.

In 2014, Klotz et al at FEM utilised computer simulation of casting and thermodynamic calculations to optimise the process parameters of casting Pt-5Ru and Pt-5Co alloys²⁹ and was significant in that ternary alloys of 950 platinum-cobalt-ruthenium alloys were explored. Improved form-filling and surface quality resulted from additions of Co to Pt-Ru alloys, the optimum amount depending on casting technique – centrifugal or tilt casting.

Maerz and Laag³³ studied six alloys in their 2016 study, Table 4, which used tilt casting (as opposed to centrifugal casting) in their trials. Two contained gallium or indium and these alloys showed higher as-cast hardness and were rated high in terms of castability. Each alloy had different strengths and weaknesses and the authors concluded that no alloy was perfect but that progress was being made. It is noted that C Hafner patented an alloy, 950 Pt-Au-In in 2013, with the use of Ir or Ru as grain refiners³⁹, which is probably the alloy referred to in Table 4

The largest range of alloys was studied by Fryé and Klotz, Table 4, who also measured mechanical properties and wear resistance of castings³⁰. They warned against use of soft alloys in cast jewellery and noted pronounced micro-segregation in Ga- and In-containing alloys which increased micro shrinkage porosity. Hot isostatic pressing treatment (HIPing) after casting eliminated porosity and restored ductility. They also noted wear was related to hardness, harder alloys wearing less.

It is clear from the foregoing that no new alloy completely met the desired casting requirements, although a database of mechanical properties of many of the casting alloys was established by Klotz and Fryé for alloys in the as-cast and in the HIPed condition³². This database has data on 13 compositions at 950 fineness and 2 at 900 fineness. As well as the conventional compositions described in Tables 2 and 4, it also includes some newer ternary/quaternary compositions, as shown in Table 5, which only lists the hardness values; perhaps, it also clarifies some of the unknown compositions documented in Table 4.

A more fundamental approach to improved casting alloy design³⁹ has been undertaken recently by Professor Glatzel and his co-workers at the University of Bayreuth and Richemont International.  They looked to develop an improved casting alloy of 950 fineness with the following requirements:

• Low casting temperature
• Small melting range
• Microstructure that is homogenous, fine-grained (100 – 150 µm) and with low porosity
• Hardness in range Hv 155-170 for wear resistance and good ductility (>30%)
• Good reflectance with a bright surface
• Alloying elements that are biocompatible and recyclable

Their benchmark alloy was the 95Pt-1.8Cu-2.9Ga which is a recent alloy development (see Tables 4 & 5). Excluding allergenic, radioactive and toxic elements, 25 possible alloying elements were selected and ranked according to a Suitability Index which comprised 4 characteristics: maximum solubility in platinum (C_max), hardness Index (H_i), melting interval index (M_ii) and liquidus temperature change index (T_lci). From these, a first iteration of 5 alloys were selected for testing and following this, a second set of 5 alloys were selected for testing. Casting was performed in a tilt casting machine. These alloys contained up to 5 alloying elements from a list including Al, Au, Cu, Cr, Fe, Ir, Mn, Pd, Rh and V. From these 10 alloys, two in the second iteration were found to be the most promising, Table 6. It is very evident that these compositions are radically different from those listed in Tables 4 and 5.  They have a hardness of HV 164 (A2) & 165 (B2) respectively compared to HV 225 for the benchmark Pt-Cu-Ga alloy. It will be interesting to see if these or similar alloys are developed to commercial status and find a niche amongst the current alloys. With the base metal alloying elements including iron and manganese, it is possible there may be tarnishing issues with such alloys, if we compare the experiences in developing alternative white gold compositions.

C] Alloys for Additive Manufacturing (3D Printing)

The development of Additive Manufacturing (3D printing) of jewellery has attracted much interest in the industry in recent years and considerable R & D has been carried out on developing machine technology, build techniques and suitable alloys. The technology involves selective laser melting (SLM) of successive layers of alloy powders, and it has become evident that such powders need to be tailored in composition to suit the process. Alloying additions of high vapour pressure metals are not desirable, for example.  In the field of carat golds, it is also important to reduce reflectivity and thermal conductivity/diffusivity to better absorb energy and inhibit heat loss through the metal, thus enhancing consolidation of the powders during laser melting. Examples of modifying carat gold alloy compositions have been discussed⁴⁰.  Regarding platinum alloys, these tend to have considerably lower thermal conductivities as has been discussed by Wright in terms of laser welding¹⁸ and Zito in terms of 3D printing of jewellery⁴¹ Work at Progold Spa on laser selective melting of 950 fineness platinum jewellery has been reported by Zito and his co-workers^41-44. In his 2014 paper⁴¹, Zito used an unspecified 950 Pt alloy powder whilst in his 2015 paper⁴³, Zito used a 950 platinum alloy powder ‘with alloying additions slightly different from the cobalt-containing alloy used in the preceding work’ but gives no further details other than to say it was not doped with semiconductor elements to reduce thermal conductivity (as was done with the carat gold alloys in his work). In the 2018 paper, in which jewellery made by SLM is compared to the same pieces made by investment casting⁴⁴, Zito notes the items produced by casting and by SLM were made in the same 950 Pt-Cu-Ga-In alloy but gives no details on actual composition. This is different from the casting alloys discussed in the earlier section, in that it contains indium as well as copper and gallium.

Thus, it appears that there is little need to develop special alloy compositions suited to 3D printing technology; the conventional alloys are acceptable and do not appear to pose any major problems.

D] Other Alloys

To conclude this paper, I note there are other recent alloy developments that appear in the patent and other literature that do not fit into the 3 preceding categories. For example, European Patent applications from Heimerle and Meule⁴⁵ describe alloys that have optimised processing properties at 950 and lower finenesses based on Pt-W-Cu –(Ru/Rh/Ir) and described as having high hardness and abrasion resistance. The Ru/Rh/Ir additions act as grain refiners.

Another patent from the watchmaker, Omega SA⁴⁶, concerns 950 platinum alloys that are cobalt- and nickel-free, based on Pt-Ir-Au-Ge- (Ru/Rh/ Pd/Sn/Ga/Re) that have mechanical properties that meet the criteria for watchmaking whilst having the colour and luminosity of Pt-Ir alloys.

CONCLUSIONS

1. There has been an evolution of – and growth in – platinum alloy compositions for jewellery application since the 1920s, with a focus on developing alloys suited to the manufacturing technologies in current use. Until the advent of the 21^st century, most platinum alloys for jewellery were based on the existing industrial alloys with the platinum -iridium alloys favoured in the early part of the 20^th century.
2. There is now a wide range of alloys available at 950 and 900 fineness levels with a spectrum of properties. Of note has been the development of heat treatable alloys containing gallium.
3. The investment casting of platinum alloys remains a major issue in terms of surface quality and defect formation, particularly gas and shrinkage porosity. The use of hot isostatic pressing post casting removes porosity and improves mechanical properties. As yet, there is no ideal casting alloy to replace the universally accepted Pt-5Co alloy..
4. There has been a major evolution in platinum alloys, particularly for investment (lost wax) casting application, in the last two decades (21^st century). A recent substantial, structured alloy development approach has produced some significantly different casting alloys containing up to 5 alloying metals It remains to be seen if these prove to be superior.
5. The new manufacturing technology of additive manufacturing (3D printing) does not appear to require special alloy compositions.

ACKNOWLEDGEMENTS

I would like to thank Massimo Poliero and his staff at Legor Srl for inviting me to present at the Jewellery Technology Forum once again.  It is always a pleasure to present at this important international technology conference.

Thanks are also due to many friends and companies in the industry for information and allowing use of pictures and tables; these include Johnson Matthey, Legor,FEM, Progold, Platinum Guild International, Hoover and Strong and Techform.

REFERENCES

1. D McDonald & L B Hunt, “A History of Platinum and its allied metals”, 1982, Johnson Matthey, Chapter 1. ISBN 0 905118 83 9
2. E A Smith, “Working in Precious Metals”, 1933. Reprinted 1978, N.A.G. Press Ltd. Chapter 15. ISBN 7198 0032 3
3. J S Forbes, “Hallmark – A history of the London Assay Office”, 1998, Unicorn Press/The Goldsmiths’ Company, Chapter 12. ISBN 0 906290 26 0
4. G Ainsley, A A Bourne & R W E Rushforth, “Platinum Investment Casting Alloys”, Platinum Metals Review, 1978, vol 22(3), 78-87
5. A A Bourne and A Knapton, US patent US4165983A, 1979/ UK patent GB58258A, 1981
6. G Normandeau & D Euno, “Understanding Heat Treatable Platinum Alloys”, 1999, Santa Fe Symposium, ed D Schneller, Met-Chem Research Inc, 73-103. See also ibid,1998, Platinum Day symposium, Platinum Guild International, vol 5, 35-41
7. J Huckle, “The Development of Platinum Alloys to overcome Production Problems”, 1996, Proc Santa Fe Symposium, ed D Schneller, Met-Chem Research Inc, 301-325. See also: J Huckle, “Choosing platinum alloys to maximise production efficiency”, Platinum Day symposium, 1995, Platinum Guild International, vol 1, 2-6,
8. J Maerz, “Platinum Alloy Applications for Jewelry”, 1999, Proc. Santa Fe Symposium, ed D Schneller, Met-Chem Research Inc, 55-71 ,
9. Maerz, “Platinum Alloys – Features and Benefits”,2004, Platinum Guild international. Download from the Ganoksin website: www.ganoksin.com/article/platinumalloys-features-benefits )
10. E M Savitskii, “Handbook of Precious Metals”, English edition ed. A Prince, 1989, Hemisphere Publishing Corp., Chapter 6. ISBN0 89116 709 9
11. P Battaini, “Metallography of Platinum and Platinum Alloys”, 2010, Proc. Santa Fe Symposium, ed E Bell, Met-Chem Research Inc, 27-49. Also: ibid, Platinum Metals Review, 2011, vol 55(2),74-83
12. C W Corti, “Jewellery – Is it fit for Purpose?: An Analysis based on examination of customer complaints”, Presented at the Jewellery Technology Forum, Held at Vicenza, Italy, January 2018 (download from Legor/JTF website)
13. C W Corti, “Jewelry – Is it fit for purpose? An analysis based on customer complaints”, 2018, Proc. Santa Fe Symposium, Ed E Bell, Met-Chem Research Inc, p163-175
14. C W Corti, “Microalloying of High Carat Gold, Platinum and Silver”,, presented at the Jewellery Technology Forum, Vicenza, Italy, 17-18^th June 2005. Publ. in conference proceedings.
15. C W Corti, “Jewellery Alloys – Past, Present and Future”, Keynote lecture presented at the 1^st Jewellery Materials Congress, Goldsmiths Hall, London, July 2019 (download from website https://www.assayofficelondon.co.uk/events/the-goldsmiths-company-jewellery-materials-congress .
16. R W E Rushforth, “Machining Properties of Platinum”, Platinum Metals Review, 1978, vol 22 (1), p2-12
17. C W Corti, “Basic Metallurgy of the Precious Metals – Part 1”, 2017, Proc Santa Fe Symposium, Ed E Bell, Met-Chem Research Inc, 25-61
18. J C Wright, “Laser-welding platinum jewellery”, 2001, Proc Santa Fe Symposium, ed E bell, Met-Chem Research Inc, p455-468. See also J C Wright, “Jewellery-related properties of platinum”, Platinum Metals Review, 2002, vol 46(2) 66-72
19. P J Horton, “Investment Powder Technology – The Present and the Future”, 2001, Proc Santa Fe Symposium, Ed. E Bell, Met-Chem Research Inc, 213-239
20. J Maerz, “Platinum Casting Tree Design”, 2007, Proc Santa Fe Symposium, Ed E Bell, Met-Chem Research Inc, 305-322
21. R Atkin, “Trouble Shooting Platinum Casting Defects and Difficulties”, 1996, Proc Santa Fe Symposium, Ed D Schneller, Met-Chem Research Inc, 327-337.
22. P Lester, S Taylor & R Süss, “The Effect of different investment powders and flask temperatures on the casting of platinum alloys”, 2002, Proc Santa Fe Symposium, Ed E Bell, Met-Chem Research Inc, 321-334.
23. U Klotz & T Drago, “The role of process parameters in Platinum Casting”, 2010, Proc Santa Fe Symposium, ed E Bell, Met-Chem research Inc, 287-325 and references therein. Also, ibid, Platinum Metals Review, 2011, vol 55(1), 20-27
24. T Fryé & J Fischer-Buehner, “Platinum alloys in the 21^st Century: A Comparative Study”, 2011, Proc Santa Fe Symposium, Ed E Bell, Met-Chem Research Inc, 210-229 and references therein. Also ibid, Platinum Metals Review, 2012, vol 56(3),155-171. An updated version also presented at the Jewellery Materials Congress, London, July 2019 (download from https://www.assayofficelondon.co.uk/events/the-goldsmiths-company-jewellery-materials-congress )
25. K Weisner, “Heat treatable platinum for jewelry”, 1999, Platinum Day symposium, Platinum Guild International, vol 6, 25-30
26. T Biggs, S Taylor & E van de Lingen, “The hardening of platinum alloys for potential jewellery application”, Platinum Metals Review, 2005, vol 49(1), 2-15.
27. C W Corti, “Metallurgy of Microalloyed 24 carat Golds”, 1999, Proc Santa Fe Symposium, Ed E Bell, Met-Chem Research Inc, p379-402; also ibid, Gold Bulletin, vol 32(2), 39-47
28. T Fryé, J T Strauss, J Fischer-Buehner, U Klotz, “The effects of Hot Isostatic Pressing of platinum alloy castings on mechanical properties and microstructure”, 2014, Proc. Santa Fe Symposium, Ed E Bell & J Haldeman, Met-Chem Research Inc, 189-209
29. U Klotz, T Heiss, D Tilberto & F Held, “Platinum investment casting: Materials properties, casting simulation and optimum process parameters”, presented at Santa Fe Symposium, 2014 but published in Proc Santa Fe Symposium, 2015, ed E Bell et al, Met-Chem Research Inc, p143-180. Also, ibid, Johnson Matthey Technology Review, 2015, vol 59(2), 95-108 & 129-138
30. T Fryé & U Klotz, “Mechanical properties and wear resistance of platinum jewelry casting alloys: A comparative study”, 2018, Proc Santa Fe Symposium, ed E Bell et al, Met-Chem Research Inc, 235-273.
31. T Laag & H-G Schenzel, C Hafner GmbH, German patent application DE10212007299A1, 17.10.2013,
32. U Klotz & T Fryé, “Mechanical properties of platinum jewellery casting alloys”, 2019, Johnson Matthey Technology Review, vol 63(2), 89-99
33. J Maerz & T Laag, “Platinum Alloys, Features and benefits: comparing six platinum alloys”, 2016, Proc Santa Fe Symposium, ed E Bell et al, Met-Chem Research Inc, 335-353
34. R Lanam, F Pozarnik, T Volpe, “Platinum alloy characteristics: A comparison of existing platinum casting alloys with Pt-Cu-Co”, 1997, Platinum Day symposium, Platinum Guild International, vol 3, 2-12
35. G Normandeau & D Ueno,”Platinum alloy design for the investment casting process”, 2000, Platinum Day symposium, Platinum Guild International,, vol 8, 41-49
36. S Grice & C Cart, “PlatOro™: The perfect marriage”, 2002, Platinum Day symposium, Platinum Guild International, vol 10, 4-7
37. S Grice, Private communication, June 2021
38. R Bertoncello & J Fischer-Bühner, Legor patent application ITM120110750A1, 2011 “Platinum-cobalt alloys with improved hardness”.
39. T Trosch, F Lalire, S Pommier, R Völkl, U Glatzel, “Optimisation of a jewellery platinum alloy for precision casting: Evaluation of mechanical, microstructural and optical properties”, 2018, Johnson Matthey Technology Review, vol 62(4),364-382.
40. U Klotz, D Tilberto & F Held, “Additive manufacturing of 18 karat yellow gold alloys”, 2016, Proc Santa Fe Symposium, ed. E Bell et al, Met-Chem Research Inc, 255-272
41. D Zito, A Carlotto, P Sbornicchia et al, “Optimisation of SLM technology main parameters in the prodiction of gold and platinum jewellery”, 2014, Proc Santa Fe Symposium, ed E bell & J Haldeman, Met-Chem Research Inc, 439-469
42. D Zito, V Allodi,, P Sbornicchia & S Rappo, “Why should we direct 3D print jewelry? A comparison between two thoughts: Today and tomorrow”, 2017, Proc Santa Fe Symposium, ed E Bell et al, Met-Chem Research Inc, 515-556
43. D Zito, A Carlotto, A Loggi, P Sbornicchia, D Bruttomesso & S Rappo, “Definition and solidity of gold and platinum jewlry produced using selective laser melting (SLM™) technology, 2015, Proc Santa Fe Symposium, ed E Bell et al, Met-Chem Research Inc, 455-491
44. D Zito, “Potential and innovation of the selective laser melting technique in platinum jewelry”, 2018, Proc Santa Fe Symposium, ed E Bell et al, Met-Chem Research Inc, 625-684
45. G Steiner, “Platinum Alloy for Jewelry”, European patents EP 2260116B1, 2014 and EP 209994181, 2007, Heimerle & Meule GmbH,
46. E Leoni et al, “Platinum alloy” European Patent EP3502286 (A1), 2019, Omega SA.

Note: Papers published in Platinum Metals Review/Johnson Matthey Technology Review can be downloaded free from the archive at https://www.technology.matthey.com/ . Many papers from the various Santa Fe Symposia can be downloaded free from the Santa Fe Symposium website archive at www.santafesymposium.org . Papers from Gold Bulletin can be downloaded from the Springer/Gold Bulletin website at https://link.springer.com/journal/13404/volumes-and-issues

a speech by Florian Bulling

Introduction

Titanium alloys are known for their high mechanical strength, low density and high corrosion resistance. Therefore, their application is mainly in the field of aerospace industry, but also in medicine as implant material. The alloy Ti-6Al-4V, also known as Grade 5 titanium is the most widely used alloy. Other titanium-based alloys are the intermetallic compounds NiTi, known as Nitinol®, which is used for its superplasticity as stent material or as actuator. Another important alloy is the intermetallic compound TiAl, which is used in aircraft turbine engines.

The excellent and outstanding properties of these alloys are opposed by the difficulties in manufacturing titanium alloys. The high chemical reactivity of titanium melts allows only cold-walled crucible melting techniques such as vacuum arc melting.

Induction melting and casting was so far compromised by crucible reactions [1-4]. A very recent review on crucibles for induction melting of titanium alloys can be found in [4]. Conventional crucible materials such as alumina or quartz are not suitable due to the decomposition of the ceramic in contact with the titanium melt. Even high stability refractories such as zirconia or yttria, which are used as crucible coatings, are not stable enough [3].

A new ceramic material based on calcium zirconate (CaZrO₃) [1, 5-7] was recently introduced. Calcium zirconate is a synthetic ceramic material that is produced by melting a stoichiometric mixture of calcia and zirconia in an arc furnace (fused CaZrO₃). Alternatively, it can be produced by in-situ reactive sintering. Calcium zirconate shows very promising properties as crucible as well as shell mold material. The present paper provides a comparison of a standard investment with yttria front coat compared to the new, silica-free shell mold and crucibles based on calcium zirconate.

Experimental

Crucibles

The production of the crucibles was in line with the procedure described by Schafföner et al. [8]. The crucibles were manufactured by cold isostatic pressing with two types of molding material consisting of pure fused CaZrO₃ (Type A) or CaZrO₃ with amounts of ZrO₂ and CaO₃ (Type D) for an in situ reaction [9]. A mandrel of steel was used to obtain the inner shape of the crucible. After decompressing and drying of the green ceramic crucibles they were fired at 1650°C for 6 h. Typical crucibles are shown in Figure 1 (left).

To produce crucibles for centrifugal casting a CaZrO₃ slurry was used to prepare a functional coating on a commercial crucible of aluminum titanate (Porzellanfabrik Hermsdorf, Germany). The coating was fired at 1450°C to avoid cracks through different thermal expansion coefficients between the stucco and the coating of the crucible. Typical crucibles are shown in Figure 1 (right).

Shell molds

The shell molds were processed from standard wax trees according to the procedure described in [1]. The wax parts and the tree setup for centrifugal casting shown in Figure 2 and Figure 3, respectively. At wax trees for tilt casting the parts were mounted at two levels of four parts each (Figure 5).

Wax trees were dipped into a calcium zirconate slurry followed by the application of calcium zirconate stucco. Six layers were applied, three fine grained and 3 coarse grained. The dipping was practiced in 2 layers per day. Each layer was dried for at least 5 h before the following layer was applied. Careful drying of the final shells was performed under controlled atmosphere in a climatic chamber at 60% humidity, at 30°C and with an air movement of 1.3 m/s for seven days. After drying, the shells were fired at 1500°C for 4 h. Before casting the shells were preheated to casting temperature. A series of shell molds for centrifugal and tilt casting is shown in Figure 4.

For comparison a commercial silica-bonded shell system, which is commercially available from Ransom&Randolph, Dentsply, USA was used. The wax parts were coated with a front coat of yttria.

Casting trials

Before casting, the crucibles were preheated in a furnace at about 200°C in order to evaporate possible humidity absorbed in the crucible. This procedure was applied to avoid cracking of the crucibles in the casting machine due to water evaporation.

For casting trials a tilt casting machine (VTC200VTi, Indutherm, Germany) and a centrifugal casting machine (TCE10, Topcast, Italy) were used. The tilt-casting machine was equipped with two rotary vane pumps connected in series and achieved a pressure of about 8×10^-3 mbar and an oxygen partial pressure of 10^‑4 mbar immediately before casting. Such vacuum level was necessary in order to avoid reactions of the titanium melt with the gas atmosphere. The casting chamber was back-filled with argon to atmospheric pressure. A batch size of up to 300 g was used for casting. The series of casting trials was carried out with the crucibles type A and D.

The centrifugal casting machine had a maximum power of 10 kW. By the fact that this machine was not especially designed for casting titanium only a low vacuum of 40 mbar was achieved, which meant that a significantly higher oxygen partial pressure remained during casting. This caused a stronger reaction of the titanium melt due to residual oxygen in the casting atmosphere. Before casting, the casting chamber was refilled with argon to a pressure of 700 mbar. With the centrifugal machine laboratory-produced crucibles of Al₂TiO₅ with a CaZrO₃ coating and commercial crucibles with modified yttria coating were tested. The maximum batch size was 100 g titanium.

During inductive heating, the metal temperature was monitored using a thermal imaging camera (Pyroview 640N, DIAS, Germany). The camera allowed an integral determination of the temperature on the surface of the melt and the subsequent evaluation of the melting process. To investigate the influence of pre-casting evacuation, overheating and dwell time on the reaction between the titanium melt and the crucibles, different parameters were applied. The pre-cast evacuation was only necessary with the tilt-casting machine to achieve good form filling. Depending on the pumping duration, a low vacuum was obtained.

Starting with a low heating power, the metal charge was heated close to melting temperature. The slow heating led to a homogeneous temperature of the rod and thus kept the time of liquid phase in crucible (exposition time) short. As determined in several casting trials, the reactivity of the titanium melt was much higher than in the solid state. When the liquidus temperature was reached, the power was increased to melt the whole material and to overheat it before casting. The dwell time means the time while all of the material was liquid. During the dwell time, the melt was heated until the desired temperature was reached. After the dwell time the casting was manually triggered. In case of the tilt-casting machine, the tilt speed was set up to 47°/s until the final angle of 90° was reached to achieve a fast filling and a low heat loss.

Microstructure, hardness and composition measurement

After casting metallographic samples were prepared to investigate the interaction of alloy and shell mold. This employed electron scanning microscopy (Zeiss, Gemini SEM 300) and optical microscopy (Zeiss, Imager Z2M).

The chemical composition was analyzed in the center of sample cross sections by glow discharge optical emission spectroscopy (GDOES) (Spectruma, GDA750) and by EDS. In addition, X-ray diffraction (XRD) was carried out to examine the phase composition of the crucibles before and after the casting process. To detect possible cracks and defects, the crucibles were investigated by X-ray computed tomography (XCT).

Results and discussion

After casting and quenching, the different shell systems showed significantly different surface appearance (Figure 5). The trees with the yttria modified R&R shell showed large residues of the shell material sticking on the surface. Due to their hardness, it was impossible to remove them by water jetting. Instead, sand blasting was required to remove the remains of the shell. The new, CaZrO₃-based shell showed a golden colored metal surface with few shell residues on the surface. This is an indication of a very limited reaction of the melt with the new, CaZrO₃-based shell material as examined in [10].

The investigation by SEM showed the different nature of reaction of the two shell systems (Figure 6 and Figure 7). At the bottom of the pictures, the typical so-called Widmannstätten structure of the titanium alloy is visible. It consists of two phases (a, dark, and b, bright). The a-phase and the b-phase have different crystal structure that are hexagonal close packed and body centered cubic, respectively [11].

Due to the reaction with the melt the refractory from the shell decomposes [12]. Oxygen is dissolved in the alloy, which stabilizes the a-phase. Therefore, a layer of a-phase is formed at the metal surface in contact to the shell, the so-called a-case. Such a-case was found for the modified R&R shell (Figure 6, left). The a-case forms a very hard and brittle surface layer, which can be removed only with great difficulty.

The residues of the shell were surrounded by metal, which explains the difficulty in the removal of shell residues. The yttria front layer that was used to limit shell reactions was not effective. Similar effects were examined with yttria-coated crucibles. The yttria layer was dissolved into the titanium melt. During cooling yttria re-precipitated at the grain boundaries (Figure 6, right). Such ceramic inclusions resulted in embrittlement.

The calcium zirconate shell also showed certain reaction with the titanium alloy (Figure 7). However, such reaction was much weaker compared to the modified R&R shell. The porous shell was not infiltrated by the melt. For this reason, it could be removed much more easily compared to the modified R&R shell. At the interface of metal and shell, the calcium zirconate started to be dissolved by the melt.

The reaction of calcium zirconate with the melt follows a certain reaction scheme [13]. Calcium zirconate decomposes into zirconia and calcia. Both refractories further decompose to their chemical elements. Zirconium and oxygen dissolve in the titanium melt. Calcium is not soluble in titanium and evaporates. As a result, the content of zirconium and oxygen are increased. The zirconium content in the surface layer of the titanium part appears brighter in the backscattered electron image (Figure 7, indicated by arrows). However, the dissolution of oxygen and zirconium did not result in the formation of a hard a-case.

The hardness and the oxygen content in cast 10mm rods were investigated by hardness and composition profiles (Figure 8). The interface of alloy and shell is defined by the position zero. Positive and negative distance values are in the metal and in the shell, respectively. Figure 8 shows results for different combinations of crucible and shell mold. Samples melted in a copper crucible (“Cu”) were prepared by electric arc melting. Oxygen content and sample hardness were clearly correlated: The higher the oxygen content, the higher was the hardness. The samples from the yttria modified R&R shell (green and black curve) exhibited higher surface hardness and oxygen level compared to those from the calcium zirconate shell (red and blue curve). For both shells the bulk hardness was reached at a depth above 300-400µm.

The melt temperature and duration play an important role for the bulk hardness of the alloy. In order to compare different combinations of melting temperature and duration a parameter was introduced, which is based on the Larson-Miller parameter (LMP) [14]. This parameter is originally used to compare diffusion controlled processes in high temperature deformation (creep). The LMP is calculated from the temperature and the logarithm of melting duration. Figure 9 shows a plot of the bulk chemical composition and the hardness over the LMP value.

It appears that oxygen and zirconium content as well as the hardness remain constant up to an LMP value of 47. The oxygen level was between the values of the feedstock and the limit given by the ASTM standard B367-09. The ASTM standard specifies no special value for the zirconium content, but a maximum concentration of 0.1 % for all other elements. Even this limit could be met with appropriate casting parameters. The hardness of the as-cast material was ca. 360 HV1, which was higher than the hardness of the feedstock (312 HV1). Such hardness increase was due to the different microstructure of as-cast material and feedstock.

At LMP values > 47 the concentrations of oxygen and zirconium increased strongly, as well as the hardness. Therefore, both temperature and melting duration have to be controlled carefully to avoid contamination of the melt. The melting range of grade 5 titanium is 1605-1660°C. A certain superheating of at least 50 K will be required to achieve sufficient form filling. The maximum LMP value of 47 can be converted into a maximum holding time of the melt in the crucible at a certain temperature. For instance the LMP = 47 equals to a holding time of 440s at 1700°C, 72s at 1750°C and only 13s at 1800°C. This indicates the high sensitivity of the reaction to uncontrolled overheating. Therefore, we have chosen to use a slow heating process that provides a homogeneous melting of the feedstock.

Besides jewelry items, the process and materials were also tested for industrial parts such as turbine wheels or small parts of glasses frames. Figure 10 shows a turbine wheel directly after casting without further surface treatment. The defect visible on the part on the left side was already present on the wax part. The feasibility of such cast parts in grade 5 titanium proves the suitability of the new shell mold for successful investment casting of titanium parts.

Summary and Outlook

A new shell mold and crucible material based on calcium zirconate was successfully tested for the investment casting of grade 5 titanium alloy (Ti-6Al-4V). In comparison to a commercial shell with yttria front coat, the new shell resulted in less oxygen contamination, less surface hardening and prevented the formation of an a-case. However, the control of the melt temperature was crucial to keep the oxygen level low. Excessive superheating and prolonged melting durations resulted in significant oxygen contamination and hardness increase. Ideally, the melt temperature should not exceed 1700°C to avoid contamination.

Further work will focus on the heat treatment of as-cast parts and the determination of mechanical properties. Different titanium alloys and other high melting and highly reactive alloys such as CoCr, Pt and Zr will be tested with the new calcium zirconate crucible and shell molds.

Acknowledgements

This IGF Project was supported via AiF No. 18293BG within the program for promoting the Industrial Collective Research (IGF) of the German Ministry of Economic Affairs and Energy (BMWi), based on a decision of the German Bundestag.

References

1. Klotz, U.E., et al., Investment casting of titanium alloys with calcium zirconate moulds and crucibles. The International Journal of Advanced Manufacturing Technology, 2019. 103(1): p. 343-353.
2. Nastac, L., et al., Advances in investment casting of Ti–6Al–4V alloy: a review. International Journal of Cast Metals Research, 2006. 19(2): p. 73-93.
3. Klotz, U.E. and T. Heiss, Evaluation of crucible and investment materials for lost wax investment casting of Ti and NiTi alloys. International Journal of Cast Metals Research, 2014. 27(6): p. 341-348.
4. Fashu, S., et al., A review on crucibles for induction melting of titanium alloys. Materials and Design, 2020. 186: p. 108295.
5. Freitag, L., et al., Silica-free investment casting molds based on calcium zirconate. Ceramics International, 2017. 43(9): p. 6807-6814.
6. Schafföner, S., et al., Advanced refractories for titanium metallurgy based on calcium zirconate with improved thermomechanical properties. Journal of the European Ceramic Society, 2019. 39(14): p. 4394-4403.
7. Freitag, L., et al., Improved Precision Casting of Titanium Alloys Using Calcium Zirconate Moulds. refractories WORLDFORUM, 2019. 11(2): p. 76-82.
8. Schafföner, S., et al., Fused calcium zirconate for refractory applications. Journal of the European Ceramic Society, 2013. 33(15-16): p. 3411-3418.
9. Schafföner, S., et al., Influence of in situ phase formation on properties of calcium zirconate refractories. Journal of the European Ceramic Society, 2017. 37(1): p. 305-313.
10. Bulling, F., Einfluss der Gießparameter auf die Eigenschaften von Feingussteilen aus Titanlegierungen, 2017, Hochschule Aalen: Schwäbisch Gmünd.
11. Pederson, R., Microstructure and Phase transformation of Ti-6Al-4V, 2002, Luleå tekniska universitet.
12. Frye, H., D.H. Sturgis, and M. Yasrebi, Basic Ceramic Considerations for the Lost Wax Processing of High Melting Alloys, in The Santa Fe Symposium, E. Bell, Editor 2000: ABQ, NM, USA.
13. Bulling, F., et al. Investment casting of high reactive and high melting metals using calcium zirconate crucibles. in Proceedings of the liquid metal processing casting conference 2019. 2019. TMS.
14. Larson, F. and M. J., Time-Temperature Relationship for Rupture and Creep Stresses. Transaction of the ASME, 1952. 74: p. 765-771.

a speech by Marco Giuseppe Andreetta

Sisma, a growth journey of more than sixty years

Open systems and relevance for jewellery additive manufacturing

Open systems are a value for the jewellery manufacturer, enabling:

• freedom of choice

→ potentially every powder manufacturer could be validated

• possibility to adapt the building parameters to each geometry

→ different geometries have different requirements. In order to exploit all the benefits of additive manufacturing it is necessary to fine tune the building strategy

A harmonized approach to precious metal 3D printing

A harmonized approach to precious metal 3D printing:

to establish a SISTEMIC COMPENTENCE

– Density > 99,9%

– Digital microstructure

– Compliance with jewellery quality standards

– Building strategies adapted to the post processing

Compatibility with material manufacturers of precious metals

Having open parameters grants compatibility with multiple precious metal material supplier, leaving the customer free to evaluate existing suppliers or propose a new one for validation.

Currently available alloys for Jewelry additive manufacturing: 

Precious metals:

Au750 White Gold

Au750 Yellow Gold

Au750 Red Gold

Ag925

Non precious metals:

Bronze9010

Stainless Steel

Titanium alloys

Partnership with Application Specialists:

The application specialist works alongside with the final customer with the machine manufacturer support.

We chose to partner with one application experts for each strategic jewellery market, in order to accomodate requests from all over the world.

Advanced parameters:

Laser  (power, scanning speed)

Hatching (hatching distance, hatching strategies, order)

Contours (number, distance)

Beam spot (diameter, compensation) 

Layer thickness (multiple layer thickness)

Protective Gas (speed, gas mixture choice)

Powders (grain size, chemical composition)

Upskin & Downskin

Advanced parameters: before and after the building process

Geometry driven parameters

Small dimension part

• Part description: thin wall section (0.7mm)
• Validation criteria: surface quality, complex geometries compliance

• Small beam spot diameter
• Material choice with smaller than usual grain size
• Easy to remove support, only supportive function

Massive part

• Part description: wall thickness changes across the part
• Validation criteria: mechanical properties, density and geometry compliance, build speed

• Medium or variable beam spot
• Supports: heat exchange, supporting and anchoring function
• Benefits from pre-heating
• Skin/core laser parameters to increase build speed

Beam spot diameter: small beam spot for special applications

“Pixel” technical sample – Bronze 90-10

▪ No correlation with conventional technologies

▪ The part is made of interconnected pieces

▪ The complete part is made in a single Ø100mm print job

▪ Combination off additive manufacturing, polishing and surface treatment (gold plating)

▪ Small beam spot parameter choice (30µm) to make the geometry possible

▪ Parameter fine tuning of the beam compensation (on the file preparation) rather than tweaking the CAD geometry

Titanium: a growing trend in jewellery

Titanium popularity is increasing in the jewellery market.

Once considered a minor metal relegated to aviation and medical industry, is now gaining importance for many reasons:

– weights a quarter of gold → bigger items are worn without discomfort

– anti-allergenic (e.g. in watchmaking Titanium can be used by whom is allergic to Nickel contained in 904L)

– can be processed to show a wide range of bold colours

Titanium: traditional technologies drawbacks

Titanium has its drawbacks for traditional machining:

Traditional processing of Titanium is costly.

Dedicated machinery is used to safely and effectively work with this alloy.

Machining Titanium usually requires:

– high torque machine and low speeds, to reduce the heat generation

– higher speeds usually generate unwanted hardening of the metal, increasing tool wear

Casting Titanium is a difficult task as well.

Titanium: advantages of 3D printing

Titanium can be 3D printed easily and safely on a well tuned machine.

Indeed, is one of the easiest material to be 3D printed:

– highly self supporting → a small amount of supports leads to increased geometry freedom and reduction of post processing

– relatively low elastic modulus → controlled distorsion during 3D printing

And, moreover, a wide range of alloys are already developed for other demanding markets.

Commonly Available Titanium alloys

Ti6Al4V – gr.23 ELI

Industry standard for aerospace and medical applications. More than 350 HV5

Ti gr.1, Ti gr.2

This two Titanium grades shares corrosion resistance, weldability, and high ductility. Almost pure Titanium, other elements are less than 0,2%. Roughly 225 HV5

Ti6Al4V – gr.5

Widely available on the market, it shares the chemical composition of gr.23 but with higher amount of Oxygen.

Serial production of hollow Titanium chain. Titanium itself helps stacking easily complex geometry with small amout of supports.

Source: A 3D-Printed Ultra-Low Young’s Modulus β-Ti Alloy for Biomedical Applications by Massimo Pellizzari, Alireza Jam, Matilde Tschon, Milena Fini, Carlo Lora and Matteo Benedetti https://www.mdpi.com/1996-1944/13/12/2792

New Titanium alloy being researched

Requirements:

Lower elastic modulus

Great fatigue resistance

Optimal corrosion resistance

Optimal biocompatibility (alloy without Vanadium)

New Titanium alloy being researched

Findings:

Lower elastic modulus was also useful to control the deformations during the printing process

–> the  new material  has even higher buildability characteristics if compared with conventional Ti6Al4V

It may be possible to completely avoid the heat treatment or at least switch to a lower temperature aging and stress relieving process

–> Possibility of using cheaper furnaces and avoid vacuum heat treatment for Titanium

New Titanium alloy being researched

Flexible Titanium applications in the luxury market

Current developments in Sisma :

• Development of new alloys
• Fine tuning of existing alloys for the LMF process
• Fine tuning of the whole process (powders, LMF, heat treatment, inert gas mixture choice) to satisfy specific market requests.

a speech by Marco Marcin Piersiak

Abstarct

CSR. Sustainability. Responsible sourcing. Conflict free. These are key words that have become increasingly important in the gold industry in recent years.
Awareness on the issues in gold mining, such as the financing of conflict, human rights abuses, unsafe labor conditions, environmental destruction and negative social impacts, has increased. This requires the industry to take a closer look at its gold supply chains and promote solutions that provide access to conflict-free, legal or responsible gold in order to minimize the reputational risks for the sector.
Additionally, consumers are increasingly concerned about the origin of the products they buy and demand improved conditions throughout the supply chain of consumer goods. This is being reflected in the consumer spending on ethical, responsible or green products which have been increasing steadily. Market studies show that ethical consumerism is growing significantly, and ethical brand values drive purchase decisions.
Responsible gold sourcing therefore is not only a business opportunity and strategy for businesses worldwide, but a “must” for those companies who want to stay relevant for future generations.
Companies that provide their clients with responsible gold products can position and distinguish themselves from others and provide consumers with a more meaningful brand experience, while improving their corporate social responsibility and contributing to the Sustainable Development Goals.

Alliance for responsible mining: Who we are?

Non-Profit Organization established in 2004

Leading global expert on gold artisanal and small-scale mining (ASM)

Experience with 150 mines in 24 countries

GOLD AND PRECIOUS METALS MINING

What about recycled gold?

A sector with challenges, but…

Mining generally has a poor reputation, and in particular artisanal mining is often associated with:

– Illegality and informality or the funding of armed conflicts

In Honduras, it is estimated that there are 2.500 informal artisanal miners, informal = don’t comply with all mining norms.(legal and economical barriers to the formalization)

– Artisanal miners often live in precarious conditions, there is poor health and safety of workers, and in the worst cases you can find child labor, accidents and deaths.

– Also, gender equality or discrimination may be common.

– ASM is one of the principal sources of mercury pollution and intoxication and you may have seen pictures of vast environmental destruction due to unorganized, illegal mining.

In Honduras : ASM mining communities use approx. 90 T of mercury / year. 

Why are all of these issues so prevalent in the ASM sector?

– Lack the enabling environment to improve their conditions: ASM often isn’t supported by the state but may be ignored, stigmatized or even persecuted

– Where mining legislation does exist its often not applicable or approriate to ASM, forcing these organizations to comply with regulations meant for large scale mining, only adding more barriers for inclusion.

– Often located in remote and unregulated áreas where the state isn’t present and regulation is taken over by locals or other groups

– They also lack access to necessary resources to perform mining in an organized, efficient manner:

– absence of  education and training to formalize.

– zero access to formal banking or finance to develop their activity

– Lack of access to efficient and environmentally friendly tools and technology 

Despite all these challenges this sector has incredible potential to contribute to local & national development. In Honduras, mining sector 100 and 150 USD Million of dollar every year. And the ASM  sector has a great role to play in this aspect an.  ASM  is a source of income for many families

Why engage with ASM?

Risks & Reputation

▪ Risks of not engaging.

▪ Excluding the sector doesn’t contribute to solving its problems but deteriorates the reputation of the sector as a whole.

Corporate Social Responsibility

▪ The biggest positive economic, social and environmental impact to be made in the gold industry is in ASM.

A holistic sourcing policy should be inclusive of gold from artisanal and small-scale mining.

Mining won’t stop

Phaedon Stamatopoulos (Director of Sourcing and Refining Argor-Heraeus)

The risks to source from ASM will be present regardless the existence of LBMA Standard v. 6, 8 or 10. If refiners do not engage with the ASM. The ASM material will take other routes and enter to international gold market. The more other routes take, the more value will be lost to LBMA members. So refiners have to engage and do it appropriately.

You choice matter!

Transforming lives through responsible artesanal and small-scale mining

But how? Buying from certified ASM

More than 370 companies from 33 countries work with Fairmined

1.6 tons and 6M USD of Fairmined Premium invested by miners

a speech by O. Balestrino

Introduzione

La presentazione si propone di evidenziare l’evoluzione dell’approccio ambientale nel corso degli anni da parte del legislatore e proporre alcune soluzioni tecniche per l’ottimizzazione e riduzione del consumo d’acqua nei processi di trattamento superficiale.

ECOTEAM spa
progetta, realizza, manutiene impianti di trattamento acque ed acque reflue.
Specializzata nel settore Trattamento e Finiture

Sviluppo della “Coscienza Ambientale” in Italia ed in Europa

• Legge 319/1976 (Legge Merli)
• D.lgs 152/2006
• 2019: “Industria 4.0”
• 2022: DNSH

La legge Merli indicava in maniera dettagliata le sostanze inquinanti, ponendo dei limiti al loro scarico nelle acque e alla loro concentrazione. Con riferimento agli scarichi, la ripartizione degli stessi ai fini della relativa disciplina e del conseguente trattamento sanzionatorio era fondata sulla loro provenienza; si disponeva inoltre che lo scarico effettuato in assenza della necessaria autorizzazione, concessa esclusivamente agli scarichi rispettosi dei limiti di accettabilità, fosse sempre soggetto a sanzione penale.

D.lgs 152 normativa di cui una sezione importante è dedicata appunto alla tutela delle acque dall’inquinamento e alla gestione delle risorse idriche.

Industria 4.0 / Ambiente

Impianti di trattamento acqua inseriti nel gruppo 2 allegato A dei materiali ammessi alla transizione 4.0, ovvero sistemi per l’assicurazione della qualità e della sostenibilità, con particolare riferimento alle due seguenti categorie:

• componenti, sistemi e soluzioni intelligenti per la gestione, l’utilizzo efficiente e il monitoraggio dei consumi energetici e idrici e per la riduzione delle emissioni
• filtri e sistemi di trattamento e recupero di acqua, aria, olio, sostanze chimiche, polveri con sistemi di segnalazione dell’efficienza filtrante e della presenza di anomalie o sostanze aliene al processo o pericolose, integrate con il sistema di fabbrica e in grado di avvisare gli operatori e/o di fermare le attività di macchine e impianti

Green Deal Europeo

Il pilastro centrale di Next Generation EU è il dispositivo Recovery and Resilience Facility che, tra i vari obiettivi, si propone di sostenere interventi che contribuiscano ad attuare l’Accordo di Parigi e gli obiettivi di sviluppo sostenibile delle Nazioni Unite, in coerenza con il Green Deal europeo.

Obiettivo «Inquinamento zero» per un ambiente privo di sostanze tossiche

Do No Significant Harm

ll principio Do No Significant Harm (DNSH) prevede che gli interventi previsti dai PNRR nazionali non arrechino nessun danno significativo all’ambiente: questo principio è fondamentale per accedere ai finanziamenti del RRF.

I piani devono includere interventi che concorrono per il 37% delle risorse alla transizione ecologica.

l principio DNSH si basa su quanto specificato nella “Tassonomia per la finanza sostenibile”, adottata per promuovere gli investimenti del settore privato in progetti verdi e sostenibili nonché contribuire a realizzare gli obiettivi del Green Deal.

Criteri del DNSH
Il Regolamento individua sei criteri per determinare come ogni attività economica contribuisca in modo sostanziale alla tutela dell’ecosistema, senza arrecare danno a nessuno degli obiettivi ambientali

1   Mitigazione dei cambiamenti climatici

    Un’attività economica non deve portare a significative emissioni di gas serra (GHG)

2   Adattamento ai cambiamenti climatici

   Un’attività economica non deve determinare un maggiore

3   Uso sostenibile e protezione delle risorse idriche

   Un’attività economica non deve essere dannosa per il buono stato dei corpi idrici (superficiali, sotterranei o marini) e determinare il deterioramento qualitativo o la riduzione del potenziale ecologico

4   Transizione verso l’economia circolare, con riferimento anche a riduzione e riciclo dei rifiuti

   Un’attività economica non deve portare a significative inefficienze nell’utilizzo di materiali recuperati o riciclati, ad incrementi nell’uso diretto o indiretto di risorse naturali, all’incremento significativo di rifiuti, al loro incenerimento o smaltimento, causando danni ambientali significativi a lungo termine

5   Protezione e riduzione dell’inquinamento dell’aria, dell’acqua o del suolo

   Un’attività economica non deve determinare un aumento delle emissioni di inquinanti nell’aria, nell’acqua o nel suolo

6   Protezione e ripristino della biodiversità e della salute degli eco-sistemi

   Un’attività economica non deve dannosa per le buone condizioni e resilienza degli ecosistemi o per lo stato di conservazione degli habitat e delle specie, comprese quelle di interesse per l’Unione

Nace

Uno specifico allegato tecnico della Tassonomia riporta i parametri per valutare se le diverse attività economiche contribuiscano in modo sostanziale alla mitigazione e all’adattamento ai cambiamenti climatici o causino danni significativi ad uno degli altri obiettivi.

Basandosi sul sistema europeo di classificazione delle attività economiche (NACE), vengono quindi individuate le attività che possono contribuire alla mitigazione dei cambiamenti climatici, identificando i settori che risultano cruciali per un’effettiva riduzione dell’inquinamento. Il quadro definito dalla Tassonomia fornisce quindi una guida affidabile affinché le decisioni di investimento siano sostenibili ed è diventato un elemento cardine nei criteri di assegnazione delle risorse europee

C24 – Manufacture of basic metals

   C24.4.1 – Precious metals production

C25 – Manufacture of fabricated metal products, except machinery and equipment

   C25.6.1 – Treatment and coating of metals

ECOTEAM

«Inquinamento zero» per un ambiente privo di sostanze tossiche

Uso sostenibile e protezione delle risorse idriche

   Un’attività economica non deve essere dannosa per il buono stato dei corpi idrici (superficiali, sotterranei o marini) e determinare il deterioramento qualitativo o la riduzione del potenziale ecologico

Protezione e riduzione dell’inquinamento dell’aria, dell’acqua o del suolo

   Un’attività economica non deve determinare un aumento delle emissioni di inquinanti nell’aria, nell’acqua o nel suolo

DNSH nel T.F.

Progettazione impianti a basso impatto

• Utilizzo di prodotti a bassa tossicità
• Progettazione di impianti efficienti
• Riuso e recupero delle soluzioni
• Scarico liquido zero

Lavaggio

Riduzione dell’acqua

La progettazione del sistema di lavaggio è legata a:

1. Processo

a) Caratteristiche della soluzione di processo

b) Numero di lavaggi

c) Tipologia di lavaggi

2. Produzione

I. Superficie

II. Obiettivo finale

Importanza dei lavaggi: Riduzione dell’acqua

Un lavaggio in cascata permette una forte riduzione della portata d’acqua necessaria ed in prima approssimazione possiamo dire che la concentrazione nei lavaggi 

DNSH e ZLD

Lo Scarico Liquido Zero può utilizzare diverse tecnologie e filosofie di progettazione ma il punto chiave è l’ultimo anello che è quasi sempre un sistema di evapo-concentrazione.

L’evapo-concentratore è un sistema che permette di concentrare delle soluzioni diluite eliminando/recuperando l’acqua.

Gli utilizzi principali sono:

1. Recupero di soluzioni diluite per essere riutilizzate come soluzioni di processo

2. Riduzione degli smaltimenti con recupero dell’acqua

EVAPO-CONCENTRATORI

Esistono diverse tecnologia di evapo-concentratori:

1.Pompa di calore

1. a serpentina immersa

2. a circolazione forzata

3. con raschiatore

2.Acqua calda

1. a singolo effetto

2. a doppio effetto

3. a triplo effetto

3.Ricompressione Meccanica dei Vapori

1. a circolazione naturale

2. a circolazione forzata

3. falling film

1. Con compressore a lobi

2. Con compressore centrifugo

CONCLUSIONI

La riduzione del consumo d’acqua, fino al punto estremo dello Scarico Liquido Zero, nei processi di trattamento superficiale persegue “l’obiettivo Inquinamento zero per un ambiente privo di sostanze tossiche”.

I costi di esercizio con le opportune tecniche possono essere molto vantaggiosi.

a speech by O. Balestrino

Preface

The presentation aims to highlight the evolution of the environmental approach over the years by the legislator and propose some technical solutions for the optimization and reduction of water consumption in surface treatment processes.

ECOTEAM spa
designs, builds, maintains water and wastewater treatment plants.Specialized in the Treatment and Finishing sector

Development of “Environmental Consciousness” in Italy and Europe

• Legge 319/1976 (Legge Merli)
• D.lgs 152/2006
• 2019: “Industria 4.0”
• 2022: DNSH

The Merli law indicated in detail the polluting substances, placing limits on their discharge into water and their concentration. With reference to discharges, the distribution of the same for the purposes of the relative regulations and the consequent sanctioning treatment was based on their origin; it was also established that unloading carried out in the absence of the necessary authorization, granted exclusively to unloading in compliance with the limits of acceptability, was always subject to a criminal sanction.

Legislative Decree 152 of which an important section is dedicated precisely to the protection of water from pollution and the management of water resources.

Industry 4.0 / Environment

Water treatment plants included in group 2 Annex A of the materials admitted to transition 4.0, or systems for quality and sustainability assurance, with particular reference to the following two categories :

• components, systems and intelligent solutions for the management, efficient use and monitoring of energy and water consumption and for the reduction of emissions
• filters and treatment and recovery systems for water, air, oil, chemicals, dust with signaling systems of filtering efficiency and the presence of anomalies or substances alien to the process or dangerous, integrated with the factory system and able to warn operators and / or to stop the activities of machines and plants

European Green Deal

The central pillar of Next Generation EU is the Recovery and Resilience Facility which, among other objectives, aims to support interventions that contribute to implementing the Paris Agreement and the United Nations Sustainable Development Goals, in line with the European Green Deal.

Objective “Zero pollution” for an environment free of toxic substances

Do No Significant Harm

The Do No Significant Harm principle (DNSH) states that the actions outlined in national NRRPs may not cause any significant harm to the environment: this is a fundamental principle for accessing funding from the RRF.

In addition, the plans must include actions which contribute 37% of the resources to the ecological transition.

The DNSH principle is based on the provisions of the “Taxonomy for Sustainable Finance” adopted to promote private sector investment in green and sustainable projects and help achieve the goals of the Green Deal.

Criteria of DNSH
The Regulation identifies six criteria for determining how each economic activity substantially contributes to protecting the ecosystem, without undermining any of the environmental goals

1   Climate change mitigation

 An economic activity must not lead to significant emissions of greenhouse gases (GHG)

2   Climate change adaptation

 An economic activity must not have an increased negative impact on the current and future climate, on the activity itself or on people, nature or property

3   Sistainable use and protection of water and marine resources

An economic activity must not be detrimental to the good health of water bodies (surface, groundwater or marine) or harm its quality or reduce its ecological potential

4   Transition to the circular economy, including waste prevention and recycling

 An economic activity must not result in significant inefficiencies in the use of recovered or recycled materials, increase the direct or indirect use of natural resources, or significantly increase waste or the burning or disposal thereof, causing significant long-term environmental damage

5   Prevention and reduction of air, water and soil pollution

An economic activity must not cause increased emissions of pollutants in the air, water or soil

6   Protection and restoration of biodiversity and health of ecosystems

An economic activity must not harm the good condition and resilience of ecosystems or the conservation status of habitats and species, including those of interest to the Union.

Nace

A specific technical annex of the Taxonomy sets out the parameters for evaluating whether different economic activities substantially help with climate change mitigation and adaptation or whether they cause significant harm to one of the other goals. Based on the Statistical Classification of Economic Activities in the European Community (NACE), the activities that can help to mitigate climate change are then determined, identifying the sectors that are crucial for an effective reduction in pollution. The framework defined in the Taxonomy therefore provides a reliable guide for making sustainable investment decisions, and has become a core component of the criteria for allocating European resources

C24 – Manufacture of basic metals

   C24.4.1 – Precious metals production

C25 – Manufacture of fabricated metal products, except machinery and equipment

   C25.6.1 – Treatment and coating of metals

ECOTEAM

«Zero pollution» for an environment free of toxic substances

Sistainable use and protection of water and marine resources 

 An An economic activity must not be detrimental to the good health of water bodies (surface, groundwater or marine) or harm its quality or reduce its ecological potential

Prevention and reduction of air, water and soil pollution

An economic activity must not cause increased emissions of pollutants in the air, water or soil

DNSH in F.T.

Low impact plant design

• Use of low toxicity products
• Design of efficient systems
• Reuse and recovery of solutions
• Zero liquid discharge

RINSING

Water reduction

The design of the washing system is linked to:

1. Process

a) Characteristicsof the process solution

b) Numbers of rinsing

c) Type of rinsing

2. Production

I. Surface

II. Final goal

Importance of rinsing: Water reduction

A cascade rinsing allows a strong reduction of the necessary water flow and as a first approximation we can say that the concentration in the washes Xn

DNSH e ZLD

The Zero Liquid Discharge can use different technologies and design philosophies but the key point is the last link which is almost always an evaporation-concentration system.

The evaporator-concentrator is a system that allows you to concentrate diluted solutions by eliminating / recovering water.

The main uses are :

1. Recovery of diluted solutions to be reused as process solutions

2. Reduction of disposal with water recovery

EVAPO-CONCENTRATORS

There are different technologies of evapo-concentrators:

Heat pump

  with immersed coil

  forced circulation

  with scraper

Hot water

  single effect

  double effect

  triple effect

Mechanical Vapour Recompression

1. Natural circulation

2. forced circulation

3. falling film

a) With lobe compresso

CONCLUSIONI

The reduction of water consumption, up to the extreme point of Zero Liquid Discharge, in the surface treatment processes pursues “the goal of zero pollution for an environment free of toxic substances“

Operating costs with the appropriate techniques can be very advantageous.

a speech by Filippo Finocchi

Title: Our Common Future – Brundtland Report

Author: World Commission on Environment and Development

Year: 1987

For the first time, the report identifies Sustainability as:

The condition of a development capable of “ensuring the satisfaction of the needs of the present generation without compromising the possibility of future generations to realize their own”

Precious Metals

Supply and Demand: Gold

Supply and Demand: Silver

Supply and Demand: Platinum

Supply and Demand: Palladium

Supply and Demand: Rhodium

Supply Sources:

Mining

Refining

Grandfathered

Kinf of Mines

Open Pit Mine

Underground Mine

Artisanal Mine

Recycled Sources from Refining

Industrial Scraps

Jewelry Scraps

Disinvestments

Central Bank Sales

Electronic Scraps

Rules and Associations

Responsible Jewellery Council

Individual provisions of the COP

Overview of the RJC CoC Standard

Sustainability on Precious Metals

PROVENANCE CLAIM 

A documented claim made through the use of descriptions or symbols, relating to Precious Metals and specifically relate to their:

Origin – Geographical origin of materials, for example country, region, mine or corporate ownership of the Mining Facility/ies;

Source – Type of source, for example recycled, mined, artisanally mined, or date of production;

Practices – Specific practices applied in the supply chain relevant to the Code of Practices, including but not limited to, standards applicable to extraction, processing or manufacturing, conflict-free status, or due diligence towards sources.

Claims supported by evidence to avoid:

• Greenwashing
• Misleads consumers
• Unfair to competitors who make legitimate efforts

All precious metals used by Legor Group S.p.A. are 100% RJC CoC compliant and 100% from recycled sources (Au, Ag, Pt, Pd, Rh)