Fatigue damage initiation mechanisms in bearing steel

This work deals with an experimental investigation of fatigue damage initiation mechanisms in high-grade, low-alloyed 100Cr6 bearing steel. The fatigue tests were carried out at rotative bending loading with parameters, frequency f = 50 Hz, stress ratio (coefficient of cycle asymmetry) R = -1, temperature T = 20 +/- 2 degrees C, in the region ranged from N-f approximate to 1.5 x 10(3) to N-f approximate to 1.0 x 10(8) cycles. The surface fatigue failure mechanism was observed in the area of low number of cycles N-f approximate to 1.5 x 10(3)-N-f approximate to 4.3 x 10(4) cycles (persistent slip bands from surface roughness), while subsurface fatigue failure mechanism was observed in the area of very high number of cycles, N-f approximate to 1.0 x 10(7)-N-f approximate to 1.0 x 10(8) cycles (from non-metallic inclusions, mostly TiN inclusions but also from Al2O3 inclusion). The paradox is that on one hand the high fatigue life is required for bearing steels, while on the other hand, the content especially titanium is not prescribed in standard for the chemical composition of this 100Cr6 bearing steel. Copyright (C) 2020 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the 37th Danubia Adria Symposium on Advances in Experimental Mechanics.

Automated summary

This work investigates the fatigue damage initiation mechanisms in high-grade, low-alloyed 100Cr6 bearing steel through experimental tests. The study reveals that surface fatigue failure is caused by persistent slip bands from surface roughness, while subsurface fatigue failure is caused by non-metallic inclusions, primarily TiN and Al2O3. Interestingly, the chemical composition standard for 100Cr6 bearing steel does not prescribe the content of titanium, despite the high fatigue life requirement for bearing steels.