The effect of laser transformation hardening on the microstructure and mechanical properties of 65Mn steel

65Mn steel is an alloy steel commonly used for manufacturing circular saw blades. In this study, CO2 continuous laser transformation hardening (LTH) was performed on 65Mn steel to investigate the effects of different laser powers on the microstructure and mechanical properties of the steel. The mechanical properties of the samples were evaluated using a tensile testing machine. The hardness and surface residual stress were measured with a Vickers hardness tester and an X-ray residual stress measuring instrument, respectively. The microstructure and fracture morphology of the samples were examined using scanning electron microscopy, and the fracture mechanism was explored. The experimental results revealed that the microstructure of the laser transformation hardened (LTHed) samples consisted of needle-like martensite, retained austenite, and carbides. The highest hardness of the LTHed samples was found to be 2.75 times greater than that of the untreated matrix. Additionally, residual compressive stress was generated on the surface of the LTHed samples. LTH significantly improved the yield strength, tensile strength, and elongation of 65Mn steel. The fracture toughness of the LTHed samples showed a decrease in porosity and exhibited a quasi-cleavage fracture morphology.