Effects of laser shock peening on the properties and microstructure evolution of laser-polished surface of Cr12 steel

Laser polishing efficiently reduces the surface roughness of die steel, but at the same time, residual tensile stress is induced on the surface, leading to crack initiation and propagation. The present study induces residual compressive stress on the laser-polished surface of Cr12 steel by laser shock peening. The surface residual stress of samples, which underwent different treatments, is measured and compared. The experimental results show that laser shock peening effectively eliminates the residual tensile stress generated by laser polishing. The compressive residual stresses of the laser-polished samples subjected to laser shock peening with 3, 6, and 9 J energies are 114.5, −138.5, and −209.5 MPa, respectively. Moreover, the surface roughness, microhardness, and microstructure evolution of the laser-polished surface with laser shock peening are investigated.