Effect of shot peening on the surface properties and wear behavior of heavy-duty-axle gear steels

Under the condition of alternating loads, high speeds and high torque levels, the wear failure on gear surface is one of the main failure modes in the heavy-duty-axle gears, which significantly affects its working life and service performance. In this paper, the shot peening method is proposed to strengthen gear steels, the effect of shot peening coverage on surface properties and wear behavior of gear steels is systematically studied. The results show that increasing shot peening coverage can obviously improve the surface properties of gear steels. Specifically, compared with the unpeened samples, the maximum compressive residual stress can be increased from 185.85 to 1095.80 MPa, the peak microhardness value can be increased from 712.3 to 850.1 HV1.0, the average grain size in the near-surface layer can be decreased from approximately 1.10 to 0.66 μm and the volume fraction of martensite in the near-surface layer can be increased from 59% to 84.99%. Meanwhile, increasing shot peening coverage can significantly enhance the wear behavior of gear steels depending on the improvement of the surface properties. Specifically, compared with unpeened samples, the average wear volume of the samples treated with the coverage of 1000% can be decreased by 52.26% and the friction coefficient can be decreased by 7.69%. Moreover, increasing shot peening coverage can affect the wear mechanism varying from adhesive wear to abrasive wear.