This paper describes the development of new 950Pd alloys with improved properties. 950Pd alloys are soft and suffer from poor mechanical properties. The newly developed alloys show superior mechanical properties, low density and bright color. They were developed based on thermodynamic simulations with a focus on improved casting characteristics. Selected alloy compositions were melted and investment cast in small batches of 50g to characterize the main properties such as melting interval, form filling, shrinkage porosity, segregation behavior, melt reactivity and age hardenability. Suitable crucible and investment materials were tested. The most promising alloys were then selected for larger casting trials. Jewelry items and tensile samples were cast and tested under different casting parameters and characterized in detail by tensile and hardness testing, wear testing, color measurement and microstructure in the as-cast and hot isostatic pressed condition. In order to transfer the results to industrial practice, pre-alloy was provided and casting trials were done under industrial conditions. Three compositions showed the most promising properties. With a Vickers hardness of 150-160HV1 in the as-cast condition, the alloys have to be considered as medium to hard.

Author: Dr. Ulrich E. Klotz and Franz Held