Impact of laser shock times on the wear resistance of 38CrMoAl steel

In order to improve the nitridation layer's quality and wear performance of 38CrMOAl steel, we put forward a combined method of laser shock processing and nitridation. Through ball milling experiments, we measured the wear performances of 38CrMOAl steel samples, which were nitridated after processing by different times of laser shocks. We also examined the microstructure and phase composition of the samples using SEM and XRD. The result shows that, with increasing times of laser shocks, the wear rates of the samples decrease firstly and increase afterwards. Moreover, we discussed the mechanism of improving wear resistance by laser shock treatment from two perspectives, namely, the microstructure and phase composition of the nitridated surface. It is concluded that laser shock processing can promote nitridation. When no new phase is formed in the nitridation layer, with increasing times of laser shocks, the sizes and number of the nitride particles in the surface increases, hence, the second diphase strengthening and the solution strengthening effects are enhanced, as well as the wear resistance is improved. However, when the laser shocks are more than a certain value, lots of nitride particles along the grain boundary will distribute with reticulation, thus reduce the wear resistance.