Plasma nitriding to selective laser sintering parts made of SCM430 powder

Selective Laser Sintering (SLS) is an attractive Rapid Prototyping process for rapidly manufacturing dies and mechanical parts. Some recent studies have applied the SLS process to molding dies but few have applied it to stamping dies because some of the mechanical properties of SLS parts, such as strength and hardness, are inadequate for stamping dies. Plasma nitriding is widely used for hardening machine components and stamping dies to give them better wear resistance.In this study, SLS parts that are strong enough to be used as stamping dies were produced by plasma nitriding parts that had been sintered from an alloyed steel powder, JIS-SCM430 (corresponding to AISI 4130). The specimens were nitrided in N2–H2 gas mixtures at various temperatures, which hardened the surface layer. The properties of this hardened layer were then investigated.The specimens sintered from SCM430 powder had very low porosity and very high density, much like wrought materials. The porosity of the SLS specimens was 1.2%. After plasma nitriding, the surfaces of the specimens had 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 were about 680 HV and 600 HV, respectively and were much higher than that of the original SLS parts — about 330 HV. Moreover, the parts sintered from SCM430 powder and then plasma nitrided showed better wear resistance than the original SLS parts. Therefore, plasma nitriding improved the wear resistance of the SLS parts.