In this study, high-strength tool steel specimens based on AISI D2 with a C content of 1.6% or more were developed by adjusting alloying elements (C, Cr, Mo, and V). Specimens were manufactured through various heat treatments such as austenitizing, quenching, and tempering processes, and their microstructure and mechanical properties are analyzed. The hardness results varied significantly depending on the alloy composition and microstructural characteristics. For example, Fe3 with increased C and Mo contents and uniform martensite and carbide microstructure has the highest hardness (862 HV, 704 HV) both before and after tempering. Among the quenched specimens, the lowest hardness (661 HV) was observed in MD2, which had a standard AISI D2 composition and exhibited a microstructure that was fine in scale but non-uniform in distribution. Among the as-tempered specimens, the lowest hardness (581HV) was observed in Fe2, which had a relatively heterogeneous microstructure despite its increased Cr and Mo contents.
Lee et al. (Tue,) studied this question.