Effect of Carbonitriding on Contact Fatigue Life and Failure Mechanism of Martensite Steel Bearing Inner Ring

Conventional heat treatment and carbonitriding+subzero+tempering treatment (carbonitriding treatment for short) were carried out on GCr15 martensitic steel bearing inner ring, and the influence of carbonitriding on the contact fatigue life and failure mechanism of the test steel was studied comparatively. The results show that the carbides in carbonitriding treated inner ring sample were more uniform, more dispersed and finer than those by conventional heat treatment, and the surface microhardness and residual stress increased significantly. The rated life L₁₀, characteristic life L_63.2 and median life L₅₀ of carbonitriding treated inner ring sample were about 5.3 times, 6.7 times and 6.6 times those by conventional heat treatment, respectively. The contact fatigue failure damage mechanism of both conventional heat treatment and carbonitriding treated inner ring samples was spalling. The initiation of subsurface cracks of carbonitriding sample was deeper, and the initiation of secondary cracks on subsurface and the expansion of main cracks were also inhibited; there by the resistance of contact fatigue was improved.