The Hardening of Platinum Alloys for Potential Jewellery Application

Pure platinum is too soft to be used for jewellery and scratches easily. Alloying platinum increases its hardness significantly. However, platinum alloys used in jewellery do need to be easy to work and thus the alloy should be sufficiently soft, but not so soft that their wear resistance is low. A good compromise would be to work with a soft alloy during jewellery manufacture, then harden the alloy so the final finished properties were improved. In order to identify platinum alloys suitable for hardening, platinum with different alloying additions was studied. Platinum alloys with additions of less than 7 wt.% of Ag, Au, Cu, Co, Cr, Fe, Ga, Ge, In, Mg, Mn, Mo, Ni, Si, Sn, Ta, Ti, V, W or Zr were examined, and the merits of each system were assessed for commercial viability. The platinum-titanium system was deemed to show the most promise.