Rolling-sliding contact fatigue failure and associated evolutions of microstructure, crystallographic orientation and residual stress of AISI 9310 gear steel

In the present study, rolling-sliding contact fatigue (RSCF) failures of AISI 9310 gear steel were analyzed sys-tematically, in terms of characterizing the fatigue life, evolution of microstructure and crystallographic orien-tation, and variation of microhardness and residual stress distributions. The RSCF experiments were conducted using a twin rollers fatigue test rig. The RSCF life of AISI 9310 steel roller decreased continuously with increasing the maximum Hertzian contact pressure, however, it could be effectively improved by additional shot peening process owing to the enhanced microhardness and compressive residual stress near the roller surface. The main fatigue damage characteristics near the roller surface were consisted of inclined cracks, micropitting, spallation and plastic deformation. Although the compressive residual stress was reduced by RSCF, there was an obvious increase in the microhardness which should be attributed to the refined microstructure, increased dislocation density as well as phase transformation from retained austenite to martensite. In addition, the accumulated plastic strain during RSCF resulted into development of several preferred crystallographic orientations corre-sponding to ideal shear texture components of body-centered cubic (BCC) materials that has been seldom reported.