Onset of fretting corrosion in biomedical implants: surface roughness evolution under contact loads and corrosive environment
Fretting corrosion of orthopedic implants leads to surface failures that induce a cascade of biocompatibility problem like inflammation and even osteolysis. At the interfaces of modular implant components femoral head-neck taper connection, surfaces are subjected to cyclic contact loadings and micro scale frictional sliding in a corrosive environment. For understanding this fretting corrosion process, multiple asperity contact experiments are conducted to characterize roughness evolution due to the combination of contact loadings and corrosion. Cobalt-chromium-molybdenum specimens with patterned surface by machining are subjected to alternating sequence of contact loading and accelerated corrosion tests. The experimental measurement of surface roughness is used to determine the roughness evolution procedure during combined influence of contact loading and corrosive environment. A roughness evolution mechanism that incorporates contact-induced residual stress development and stress-assisted dissolution is proposed to elucidate the measured surface deformation.