Effect of feedstock bimodal powder mixture and infiltration process on mechanical behaviour of binder jetting processed 316L stainless steel

Abstract

Binder jetting additive manufacturing (BJAM) is a widely studied technique fabricating metal parts. In this study, bimodal 316L stainless steel powder mixture of coarse (D50 – 34.1μm) and fine (D50 – 6.28μm) powders were designed for BJAM. Infiltration was used to improve the density of BJAMed parts. Bimodal powder mixture showed clear advantage over unimodal powder system on density and mechanical property of BJAMed parts. Upon solid-phase sintering, BJAMed 316 stainless steel of bimodal powder mixture (9:1 mass ratio of coarse to fine powder) showed relative density 97.19% and tensile strength 343.62 MPa, as compared with relative density 84.55% and tensile strength 291.59 MPa for pure coarse powder. For the same bimodal powder mixture, bronze infiltration, compared with solid-phase sintering, resulted in noticeably higher relative density 99.92% and tensile strength 621.63 MPa. Compared with solid-phase sintering, infiltration significantly reduced the volumetric shrinkage.