The role of VC and Fe3Mo3C in strengthening hot work die steel: Insights from first-principles calculations

• A novel H13-M steel, replacing VC carbides with Fe 3 Mo 3 C, exhibits significantly improved thermal stability. • H13-M steel shows 27.5 % higher tensile strength at 600 °C than H13. • Fe 3 Mo 3 C carbides form stronger interface bonds with the Fe matrix than VC. • W doping enhances carbide adsorption and interfacial bonding in H13-M steel. Carbides, as the strengthening source, dominate the mechanical behavior of hot work die steel and can be influenced by factors such as carbide type, interfacial bonding, and others. In high-temperature environments, the formation of thermally stable carbides, such as Fe 3 Mo 3 C, contributes to enhanced performance. This phenomenon is particularly evident in H13-M, a novel modification of H13 steel designed to improve high-temperature stability. The present study investigates the effects of primary carbides, VC and Fe 3 Mo 3 C, on the microstructure and mechanical properties. First-principles calculations are further employed to explore the differences in thermal stability, interfacial bonding strength, and atomic adsorption behavior. The results indicate that the tensile strength of H13-M exceeds that of H13 steel by 27.5 % at 600 °C. Microcracks in H13 steel typically initiate at the VC/Fe interface, whereas Fe 3 Mo 3 C carbides in H13-M exhibit superior formation stability and stronger interfacial bonding. The addition of W further enhances the Fe 3 Mo 3 C carbides' ability to adsorb iron atoms and strengthens the carbide/Fe interface, providing effective nucleation sites for martensitic transformation, promoting grain refinement, and improving high-temperature mechanical performance. This study provides both theoretical insights and experimental evidence to support the regulation and design of carbides in hot work die steels.