Enhanced mechanical and wear properties of a modified H13 hot work die steel through controlled formation of M6C and stabilization of M2C

The superior mechanical properties and wear resistance above 600 °C are essential for hot work die steels used in the preparation of aluminum alloy die-castings. The type, morphology, spatial distribution and stability of carbides play a crucial role in enhancing the strength and high-temperature performance of die steel, and effectively regulating the relationship between the physical characteristics of carbides and mechanical properties remains highly challenging. In this paper, an improved H13 steel (H13-M) was prepared by reducing the contents of C, Si and Cr while adding Mo, W, Ni and Co to promote the formation of M 6 C carbides and stabilize M 2 C carbides, thereby enhancing mechanical properties, refining grain structure, and ultimately yielding an excellent balance between strength and toughness. After tempering, the coarsening of carbides was significantly inhibited, and the M 2 C carbides of H13-M steel were finely and uniformly dispersed in the matrix. High-temperature tensile and hardness tests have confirmed that the H13-M steel exhibits superior strength and tempering softening resistance compared to the traditional H13 steel. The results indicate that the wear resistance of H13-M steel is significantly improved, particularly by 2.28 times at 700 °C, which is attributed to the enhanced stability of M 2 C carbides strengthening the matrix. In addition, a more uniform and stable tribo-oxide layer was formed in H13-M, significantly reducing surface recrystallization and wear damage.