抄録
ABSTRACT
Optimum conditions for laser irradiation to achieve fully dense high-carbon steel selective laser melting (SLM) specimens have been investigated as a function of carbon content in steel powders using steel powders with different carbon contents of 0.33 − 1.04 mass% C. Full densification is easily achieved by SLM processing for all high-carbon steel powders. The energy density during the SLM process necessary for full densification decreases as the carbon content increases from 400 J/mm3 for 0.33 and 0.49 mass% C to 267 J/mm3 for 0.76 and 1.04 mass% C, which is considered to be attributable to the increased wettability of molten Fe – C alloys on steel powders and sintered specimens for the higher carbon contents. Moreover, SLM specimens that are strong enough to be used as stamping dies are produced by plasma nitriding specimens that have been sintered from an alloyed steel powder, JIS-SCM430. After plasma nitriding, the surfaces of the specimens have a compound layer, the so-called “white layer”, composed of ε – Fe2−3N and γ’– Fe4N. The surface hardness of the specimens plasma nitrided at 773 K and 823 K are about 680 HV and 600 HV, respectively and are much higher than that of the original SLM specimens – about 330 HV –.
