Alloys for Orthopaedic Implant Use

Abstract

The paper compares four alloys in orthopaedic implant use on the basis of their performance in laboratory tests. The alloys compared were cast Co–Cr–Mo, powder metallurgy (PM) Co–Cr–Mo, Ti 318 and Ti 550. Tensile, corrosion fatigue, and corrosion tests were carried out and the effect of heat treatment and of surface treatment was investigated. The corrosion fatigue tests ranked the alloys in the following order of merit (1) Co–Cr–Mo (PM), (2) Ti 550, (3) Ti 318, and (4) cast Co–Cr–Mo. The corrosion tests demonstrated for cast Co–Cr–Mo the effect of passivation, steam sterilization, and texturing, and for Ti 318 the effect of oxidizing, anodizing, and acid etch/shot peening. It was concluded that for joint replacement applications requiring the highest corrosion fatigue strength regardless of cost and neglecting the possible importance of elastic modulus, Co–Cr–Mo (PM) was best. For applications requiring ease of manufacture and allowing a lower corrosion fatigue strength, cast Co–Cr–Mo was the material of choice. For most other applications and in particular where high corrosion fatigue strength at a reasonable cost was required, the Ti alloys offered worthwhile advantages.