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Abstract

A comprehensive search has been made for alloying elements which could be effective decolourizers in an 18 carat (i.e. 75 wt-% gold) alloy. Although 16 potentially suitable elements were identified, assessment of experimental binary alloys revealed that only two of these elements, Ni and Fe, were acceptable as major alloying elements in an 18 carat, castable white gold jewellery alloy having a combination of properties which manufacturing jewellers currently believe to be ideal. The major shortcoming of Au–Ni alloys was that they were hard and work hardened rapidly but these disadvantages could be overcome effectively by adding cobalt. More complex 18 carat golds based on Au–Ni–Co alloys were designed using the information previously derivedfrom the binary gold-based alloys. Subsequently, alloys in the composition range 75Au–7–1 2Ni–7–12Fe (with Ni+Fe = 16−19)−2−3Co−2−3Cr−2−3In (in wt-%) were identified as having an improved combination of colour and hardness over those of existing commercial, castable 18 carat white golds.

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Alloying additions for 18 carat white gold jewellery alloys

Abstract

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References