Microstructure variation and local plastic response of chrome molybdenum alloy steel after quasi rolling contact fatigue testing

This work presented the microstructure variation and local plastic response of chrome molybdenum alloy steel under quasi rolling contact fatigue (quasi-RCF) testing. The quasi-RCF testing means using the similar method of actual RCF to introduce obviously local plastic deformation and microstructure variation on surface layers of materials. After quasi-RCF testing, the microstructure were observed using optical microscope and scanning electron microscope (SEM) from both the top surface and cross section. Based on microstructure analysis, the deformation volume of materials after quasi-RCF testing were calculated. The local plastic response was demonstrated by the unique local strain-stress curve and strain hardening exponent obtained via experimental measurements and simulation prediction. One hand, the increase in the hardness of plastic zones due to quasi-RCF testing was measured by a Vickers indenter. The other hand, based on the virgin hardness and elastic modulus, some possible local stress-strain curves were obtained. Then according to the possible local stress-strain curves, finite element analysis was introduced to predict the increased hardness. Comparing the increased hardness obtained by experiments and prediction, the unique local strain-stress curve and strain hardening exponent of chrome molybdenum alloy steel were determined. All results were discussed in detail.