Improvement of mechanical properties of dissimilar spot-welded joints of additively manufactured stainless steels

Abstract

The dissimilar resistance spot welding of additively manufactured steel to conventional automotive steel has attracted significant attention from automotive manufacturer. However, the mechanical properties of dissimilar spot welds could be affected by the printed properties of additively manufactured steels, limiting the further application of 3D printing process in auto-body assembly line. This paper proposed an approach to improve the mechanical properties of spot-welded joints of additive manufactured steels by the design of binder jetting printed steels with the addition of nanoparticles. Cu-Sn nanoparticles have been injected to the stainless steel via binder jetting process, aiming to fill the voids between steel particles and reduce the microstructure heterogeneity in the spot welds. The microstructure evolution, sintering behavior of nanoparticles and mechanical properties of resistance spot welded stainless steel were characterized and analyzed. The sintering behavior of Cu-Sn nanoparticles during welding process attributes to the formation of transition zone with homogenous microstructure, resulting to the improvement of hardness property and lap-shear strength of spot-welded joints. Compared to the spot welds of selective laser melting printed stainless steels, the resistance spot welded stainless steel via binder jetting process shows better mechanical properties with 48 % increase of energy absorption and 19 % increase of peak load.