Effect of shot peening on microstructure and contact fatigue crack growth mechanism of shaft steel

In this study, C53 steel was shot peened with different process parameters. The effects of shot peening pressure, coverage and shot diameter on surface hardness, roughness and residual stress of C53 steel were discussed. The effect of different shot peening parameters on the rolling contact fatigue property of C53 steel was analyzed. The results show that the coarse grains are refined into nanocrystals by shot peening, and a large number of dislocation tangles are formed. With the increase of shot peening strength, the surface hardness of C53 steel increases to 712.8 HV0.2, with an average increase of 18.3%. The maximum residual compressive stress is −677 MPa, which is 5.7 times of the original sample. And the surface roughness increases obviously. Due to dislocation tangles and nanocrystalline strengthening, the rolling contact fatigue life of C53 steel increases obviously after shot peening, but the fatigue life decreases with the increase of shot peening strength. It is found that there are two modes of rolling contact fatigue crack propagation: intergranular growth and lamellar. •Improving rolling contact fatigue life of shaft steel by shot peening.•The dislocation density increases obviously after shot peening.•Dislocation tangles leads to the formation of nanocrystals.•Crack closure mechanism of rolling contact fatigue.