Abstract
By use of reduced and carburized starting powder with a composition of SKH57, and vanadium carbide (VC) powder, tool steels having higher VC content than that in SKH57 were vacuum-sintered, HIP-ed and finally heat-treated. The mechanical properties such as hardness and transverse-rupture strength (σm) at room temperature were studied in detail mainly as a function of vanadium (or VC) contents in the range from 3.5 to 18.5 mass%V.
The hardness and σm increased and decreased with increasing vanadium or VC content, respectively. As for the σm, it was found that the value of about 4.8 GPa of SKH57 dropped to that of 3.0 GPa, according to the increase in vanadium content from 3.5 to 18.5 mass%. It was noted that σm was controlled by the size of structural defect, that is, the segregated area of MC type carbides influenced mainly by the vanadium content, excepting the carbide structure, sintering and quenching temperatures, etc. The discussion as for the reason why such a structural defect as a fracture source develops in sintered tool steels, has been given.
