Effect of laser shock peening on plasma nitriding microstructure and properties of H13 steel

Laser shock peening (LSP) was conducted on H13 steel prior to plasma nitriding (PN). The optical microscopy (OP), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), microhardness tester and ball-on-disk wear tester were employed to investigate the microstructure and properties of plasma nitrided H13 steel coupled with LSP processing. The results show that a large number of dislocations, as well as dislocation cells and nanocrystals composed of high-density dislocations, are observed in H13 steel after LSP treatment. Compared with the PN sample, the diffraction peak intensities of the Fe3N phase in the LSP + PN sample are slightly enhanced and the diffraction peaks shift to the right as a whole. Compared to the PN sample, the LSP + PN sample exhibits significant improvements in various aspects. Specifically, the white bright layer and diffusion layer of the LSP + PN sample increased by approximately 25 % and 119.4 %, respectively. Additionally, the thickness of the effective hardened layer increased by around 50 %, and the microhardness increased by approximately 31.3 %. The LSP + PN sample has the better wear resistance than that of the PN sample, with the friction coefficient, wear scar width, wear volume, and wear rate reduced by 11.1 %, 8.4 %, 7.9 %, and 7.3 %, respectively. Through parallel experiments, the experimental error is controlled within 2 %.