Effect of laser scanning speed on the thermal-mechanical coupling field of laser remelting of valve seat

Abstract

A numerical simulation model for the thermal-mechanical coupling of laser remelting of valve seat was established. The changes of thermophysical properties of the material with temperature, latent heat of phase transformation, and the absorption rate of laser energy on the surface of the material were considered in the model. The results showed that as the laser scanning speed increased, the maximum temperature and the area of the molten pool decreased, and the cooling rate of the molten pool increased. In the laser irradiation area, the temperature gradient in the molten pool decreased and the temperature gradient in the phase transformation region near the molten pool increased. When the laser scanning speed was increased from 1 mm/s to 4 mm/s, the circumferential residual stress was increased from 132 MPa to 183 MPa, and the radial residual stress was increased from 20 MPa to 51 MPa. In the laser remelting process, there was a competitive relationship between the increase in the deformation trend caused by the increase in the temperature amplitude and the decrease in the deformation constraint due to the decrease in the temperature gradient, resulting in a reduction in the residual stress accompanying the decrease in the laser scanning speed. The change trend of the simulation results was basically consistent with the experimental results, which showed the effectiveness of the simulation model.