Laser shock peening induced mechanical properties enhancement of 50CrVA alloy

Abstract

Laser shock peening (LSP) was implemented to treat aircraft landing gear 50CrVA alloy to improve mechanical properties. The sensitivity investigations of time step and mesh size were used to benchmark the 3D finite element method (FEM) model. Based on the established FEM model, the dynamic propagation characteristics of the shock wave inside the sample were predicted. The influence of laser energy and spot diameter on the residual stress field was further investigated. The numerical results indicate that regulating two critical LSP parameters can effectively improve the compressive residual stress (CRS) of metals, and the spot diameter has a greater effect than the laser energy in improving the uniformity of the CRS distribution. After that, the influences of LSP on the CRS field, microstructure, and mechanical properties were experimentally studied. After LSP treatment, the surface CRS reached 494.8 ± 31.8 MPa with an affected depth of about 400 μm. The phase composition was not changed by LSP treatment, but it weakened texture strength and refines grains. Under the impact of grain refinement and CRS, the average surface microhardness of the 50CrVA alloy reached 355 HV, indicating an increase up to 5.3 %. The ultimate tensile strength and yield strength were increased by 11.3 % and 14.5 %, respectively, which were in contrast to the unchanged elongation. This work verifies the feasibility of mechanical properties enhancement of 50CrVA alloy by LSP.