Influences of laser remelting on mechanical performances of AISI4140 steel

Abstract

Laser remelting is a promising in-operando method to improve surface quality and eliminate defects simultaneously in the laser-powder bed fusion process. In this study, the optimal processing parameters for laser remelting and the influences of laser remelting on porosity, microcracks, surface roughness, microhardness and mechanical properties of the AISI 4140 steel manufactured by laser-powder bed fusion were investigated. The results showed that laser remelting improved the relative density to 99.6% and defects in the microstructure changed from lack of fusion to keyhole morphology as the number of remelting steps increased. The roughness on the upper surface was reduced by 73% after remelting, but the roughness on the lateral surfaces deteriorated by 4.5% when remelting twice. Specimens built in the transverse orientation and treated with a single remelting step exhibit the highest tensile strength (1277 MPa). Furthermore, there is a slight improvement in the fatigue limit after remelting once. However, laser remelting in the manufacturing process did not eliminate microcracks.