Influence of roughness on surface instability of medical grade cobalt–chromium alloy (CoCrMo) during contact corrosion–fatigue

Surface roughness and contact load play a major role in contact corrosion–fatigue phenomena that accelerates corrosion pits on the stressed surface area. The local yielding and stress concentration will be produced when the rough surface is brought into cyclic contact. Subsequently, the selective electrochemical attacks on the stressed surface will lead to the roughness evolution during environmental corrosion. The continuous roughness evolution by the stress-assisted dissolution will ultimately nucleate microcracks on the surface. In this article, a new evaluation method was introduced to identify the thermodynamic driving forces responsible for the stress-assisted dissolution. In order for complete understanding of the mechanical and electrochemical response of materials surface during contact corrosion–fatigue, finite element calculations and contact corrosion–fatigue experiments were performed on textured medical grade cobalt–chromium–molybdenum (CoCrMo) specimen surfaces. Consequently, the quantitative model of roughness evolution was developed to predict contact corrosion–fatigue damage of CoCrMo surface.