Interface stability control of MC/α via vacuum induction heating to enhance high-temperature strength of H13 hot working die steel

• The tensile strength of H13 steel is enhanced to 688 MPa at 650 °C following processing via vacuum induction heating. • Induction hardening at 1100 °C is found to significantly improve the thermal stability of MC carbides in H13 steel. • The superior high-temperature strength is primarily attributed to the coherent interface between MC carbides and the matrix. H13 hot-working die (HWD) steel is extensively employed in demanding industrial applications. However, it faces a persistent challenge in simultaneously achieving high-temperature strength enhancement while maintaining satisfactory toughness. In this study, H13 steel was processed using controlled vacuum induction heating (VIH) protocols with tailored quenching temperatures. The results revealed that, under a quenching temperature of 1100 °C (VIH-2), the tempered steel exhibited a significant enhancement in high-temperature strength at 650 °C, achieving 688 ± 10 MPa, while retaining excellent impact toughness. This improvement was attributed to the strengthening contribution of thermally stable MC nano-carbides. In the VIH-2 treated H13 steel, the MC carbides were observed to be finely distributed, with a high volume fraction. Notably, these carbides maintained a Baker-Nutting orientation relationship with the matrix and formed a coherent interface, even after high-temperature deformation at 650 °C. The stable interface relationship significantly increased the dislocation pinning effect of MC carbides at elevated temperatures, thereby reducing stress concentration at grain boundaries and mitigating fracture behavior. Consequently, VIH, an efficient and precise heat treatment technique, is particularly well-suited to meet the stringent elevated-temperature property demands required for HWD steels.