Study on fatigue and wear behaviors of a TiN coating using an inclined impact-sliding test

A new ball-on-plate inclined impact-sliding test method was developed to investigate wear phenomena of coated dies under simulated automotive stamping conditions where the stamping die material undergoes a combination of impact and sliding forces. The test coupon in this study was a TiN-coated M2 steel disc. A bearing steel (AISI 52100) ball with a diameter of 10 mm was used as the counterface material. Each cycle of the testing load consisted of an impact force (Fi) and a pressing force (Fp). Tests of different impacting and sliding cycles were conducted to observe progressive failure processes. The severity of the coating failures was investigated through electron microscope observations on the coating surfaces where the impact-induced crater and sliding-induced wear track existed. It was found that the coating failure behaviors included fatigue cracking, chipping, peeling and material transfer. The test results also suggested that the fatigue cracks initiated the chipping and peeling when the cracks formed networks.