Surface Hardness Improvement of AISI D2 Tool Steel by Laser Transformation Hardening Process Using High-Power Disk Laser

The remote laser phase transformation hardening process is an effective and fast self-quenching method of surface modification to provide a uniform hardening depth over the treated surface. To enhance the surface integrity of the AISI D2 tool steel, a robot-assisted laser hardening process using a high-power disc laser was applied in this work. Using a constant power strategy, the D2 steel flat specimens were selectively processed by a laser phase transformation hardening technique. The effects of laser power and scan speed on the surface roughness, hardness, and hardening intensity were studied. The scan speed from 9 to 15 mm/s and laser power from 1050 to 2550 W were selected to estimate the influence of the related effective parameters on surface hardness improvements. The results indicated that the hardness HV values in the subsurface layer achieved 550–670 HV by the optimized laser heat treatment parameters.