Effect of microshot peened treatment on the fatigue behavior of laser-melted W6Mo5Cr4V2 steel gear

In this paper, W6Mo5Cr4V2 steel gear tooth flank was firstly melted by laser irradiation, and then treated by microshot peening (MSP) with shot particles of different materials and peening time. The materials of shot particles were high-carbon cast steels and ceramics. The peening time was from 20 s to 100 s. The fatigue behavior of gear was tested using Forschungsstelle für Zahnräder und Getriebebau (FZG) back-to-back spur gear test machine. The experimental results have showed that the microhardness of gears increased, and the surface roughness of gears decreased after microshot peening treatment. In addition, the residual stress state in the near-surface layer of microshot peened gears was changed from tensile stress to compressive stress. The microshot peening treatment has improved the fatigue strength of gears in comparison with gears undergoing the laser surface melted (LSM). The material of microshot particle influenced the fatigue behavior of gears going through laser surface melting and microshot peening (LSMMSP). The fatigue properties of LSMMSP gears did not enhance with an increase in shot peening time. The effects of the relaxation mechanism of the compressive residual stress on the fatigue performance of LSMMSP gears have also been discussed. Retained austenite has played a positive role in improving the fatigue limit of LSMMSP gears.