Degradation of TiN coatings under cyclic loading

Degradation of TiN coatings under cyclic contact loading was investigated by repeatedly loading with a 5 μm radius spherical-tipped conical diamond indenter to loads of up to 400 mN. Methods were established to eliminate the effects of creep and thermal drift to obtain data representing the degradation in the films. Based on microstructural observations of cross-sections prepared using FIB milling, it is proposed that cyclic degradation of the coating occurs via frictional degradation at the columnar grain boundaries. Existing models describing indentation are extended to describe the contact fatigue of TiN.