Investigation of rolling contact fatigue lives of Fe–Cr alloy coatings under different loading conditions

The aim of the present study is to address the rolling contact fatigue (RCF) life and behavior of thermal sprayed coatings. The Fe–Cr alloy coatings and Ni–Al alloy coatings were prepared by a plasma spray device as the surface coating and undercoating on steel substrates, respectively. RCF tests were conducted using the ball-on-disc tester under four kinds of loading conditions. The failure mechanisms were investigated on the basis of worn surface observations of failed coated specimens. The RCF lives of Fe–Cr coatings were evaluated by means of Weibull distribution plots. The results show that the contact stress obviously influences the RCF life and failure behavior of the Fe–Cr coatings. The lives decreased as the contact stress increased. At the same time, the main failure modes of the coatings changed from abrasion and spalling to delamination. The failure mechanisms of coatings are associated with the micro-defects, the bond strength of the coatings and the orthogonal shear stress (OSS) within the coatings. The S–N curve, based on RCF life data by using statistical approach, is helpful for the design of hard coatings.