Investigation into the densification of AISI304 parts fabricated by hybrid powder metallurgy techniques

Complex and high-performance parts of metal and ceramics can be fabricated by selective laser sintering/isostatic pressing (SLS/IP), in which cold isostatic pressing (CIPing) is introduced into SLS followed by high sintering (HSing) and hot isostatic pressing (HIPing). In this paper, the mechanisms of action of CIPing pressure and HSing temperature on relative densities of AISI304 parts fabricated by SLS/IP are respectively investigated. Based on the liquid sintering theory, the effects of trace FeB on their relative densities, metallurgical structures and mechanical performances are likewise analyzed. Results show that there is a minimal threshold of CIPing pressure for AISI304 parts in the process of SLS/IP, which is about 400 MPa. Their relative densities approximates certain value with an increase of HSing temperature from 1250°C to 1350°C, which are improved while their mechanical performances worsen with an increase of FeB content from 0.5% to 5.0%, and their metallurgical structures consist of eutectic (α-Fe, Fe₂B) and (Ni,Ni₃B) besides austenite (Fe,Cr,Ni,C). Although their strengths are better when FeB content is 0.5wt%, their elongation percentages are lower, which is only about 8%.