4. Conclusion In the present study, the 17-4 PH coating was prepared on 27SiMn steel via LC technology, and the coating was strengthened by post LSP treatment under different laser energies. The effect of LSP on the microstructure and wear behaviors of the LC coating was systematically studied, and the following conclusions can be drawn. (1)There is a small amount of residual austenite present in the laser cladding layer, and all residual austenite was transformed into martensite after LSP treatment. The distance and space between adjacent dendrites gradually decrease, and the dendrites and dendrites become closer. LSP treatment did not bring additional laser remelting process to the cladding layer, and the severe plastic deformation caused by laser shock waves significantly refined the grains of the cladding layer. EBSD and TEM analysis showed that LSP introduced severe plastic deformation on the top surface of the coating to form dislocation structures. It promoted the formation of sub-grain boundaries in coarse grains and refined the grains through dynamic recrystallization. The grain size decreased with the increase of laser energy, and the average grain size decreased from 4.37 μm to 1.81 μm when the laser energy is 9 J. (2)LSP can introduce compressive residual stress on the top surface of the coating with a maximum value of 500 ± 10 MPa when the laser energy is 9J. The microhardness of the coating increased significantly after LSP treatment, and it increases with the increase of laser energy, with a peak value of 450±8HV. The effective depth of LSP on residual stress and microhardness was measured as about 1–1.1 mm. (3)After LSP treatment, the COF and wear rate of the 17-4 PH coating were significantly reduced, and the wear mechanism changed from dominative adhesive to slight abrasive wear. The improvement of microhardness and wear properties after LSP was attributed to the combined effects of Hall-Petch and Taylor hardening strengthening.