Rolling contact fatigue behavior of plasma-sprayed CrC–NiCr cermet coatings

The aim of the present study was to address the fatigue behavior and failure mechanisms of plasma-sprayed CrC–NiCr cermet coatings in rolling contact. Rolling contact fatigue (RCF) tests were conducted for the coatings under two different tribological conditions of contact stress at room temperature. For all tests, the thicknesses of the coatings were controlled to be about 100 μm. At a given contact stress, 13 rolling contact tests were performed to obtain the statistical result. The Weibull distribution plots of fatigue life data of the coating specimens were obtained. Experimental results showed that the life parameters, such as the characteristic life, decreased with increasing the contact stress. Moreover, the RCF life data of the coatings tested at higher contact stress exhibited higher scattering. Worn surface observations of the failed coating specimens showed that the failure modes of coatings could be classified into four main categories, i.e., surface abrasion, spalling, delamination within the coating and at the coating/substrate interface. When the contact stress was low, most of the coating specimens failed due to the delamination within the coating. However, the interfacial delamination was the main failure mode of the coatings at high contact stress. The failure mechanisms of the coatings were associated with the microstructure and the bonding strength of the coatings, the depths of the orthogonal shear stress and the maximum shear stress.