'PM' used for Bio-Metallic Materials. Application to a Cobalt base Alloy with 28 Cr and 6Mo

摘要

Cobalt-Chromium alloys (in particular 28%Cr, 6%Mo) have been used for many years in cast form for surgical implants. It soon became evident that the performance of this alloy could be greatly increased by using it in the wrought condition as bars and closed die forgings for subsequent machining into parts. Melting by the VIM + ESR route means that the metallurgical quality is excellent, and extremely tightly controlled; however, machining remains difficult. The development of high carbon grades to give improved tribological performance has also brought to light difficulties in controlling carbide size and distribution. The production of such alloys by powder metallurgy and HIPping is a right solution to these technical difficulties and has also been shown to be favourable from an economic point of view. The many trials and production runs undertaken to date have demonstrated equivalence with the other methods of production, and have opened the door to other possibilities: 1. Increase in certain properties by micro-alloying 2. Production of "as-HIPped" parts 3. Powder production for porous coating of the implants.