Surface hardening of AISI 4340 steel by laser linear oscillation scanning

This study investigated the surface hardening of AISI 4340 steel by linear oscillation scanning with a fibre laser. Various frequencies and amplitudes of oscillation were used under laser power of 2020 and 3020 W. Microscopic evaluation was done, and the effect of oscillation frequency on the hardened depth was examined. Hardness profiles were measured along the centre of the irradiated track toward the feeding direction of the laser, across the irradiated width and into the depth below the irradiated surface. The homogeneity of hardness and hardened depth with different processing parameters was investigated. The hardness profiles were compared with the results obtained with conventional single track hardening.