The Effect of Stress Relieving Temperature on Mechanical Properties, Residual Stresses and Lattice Parameter Evolution of L-PBF High-Carbon Tool Steel D2

This study investigates the impact of stress relieving temperature on the mechanical properties, residual stresses, and lattice parameter evolution of laser powder bed-fused (L-PBF) high-carbon tool steel D2. The objective was to determine the optimal stress relieving conditions to improve material performance. Methodologically, L-PBF was conducted at a preheating temperature of 360 °C, followed by heat treatment at temperatures of 550, 600, and 650 °C for two hours. The study included assessments of hardness and residual stress profiles, tensile properties, and an analysis of fracture surfaces. The results indicated that the maximum hardness achieved was 625 HV1, with a yield strength of 1441 MPa and a tensile strength of 1813 MPa at 600 °C. X-ray diffraction analysis revealed the formation of M7C3 carbides during heat treatments, which demonstrated at least partial coherence with the body-centered cubic (BCC) phase, as indicated by changes in the lattice parameter. Notably, the as-manufactured samples exhibited significant residual stresses nearing 800 MPa, which were reduced through low-temperature tempering. These findings confirm that high-carbon tool steel can be effectively manufactured with L-PBF and that substantial residual stresses can be managed with comparatively mild heat treatment.