Interface analyses and mechanical properties of stainless steel/nickel alloy induced by multi-metal laser additive manufacturing

Abstract

Multi-metal laser additive manufacturing is an emerging technology to fabricate complex components with excellent comprehensive performances. In this study, stainless steel/nickel alloy multi-metal has been induced by laser direct energy deposition. The microstructural evolution, compositional segregation, and crack formation at the interface of the two metals have been investigated by optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, electron backscattering diffraction, and microhardness test. The results show that the microstructure morphologies are predominated by equiaxed dendrite and columnar dendrite for stainless steel and nickel alloy, respectively. The Marangoni convection effect promotes the serious compositional segregation of stainless steel on the nickel alloy side and serious segregation of 316L SS occurs locally in near the IN 718 side of the interdiffusion region. During the cooling process, the segregated stainless steel has a lower solidification temperature than the surrounding nickel alloy. The compositional segregation and different physical properties of the two metals are the main causes for the ductility dip cracking near the interface. During tensile deformation, the multi-metal fractures on the stainless steel side, and the ultimate tensile strength and elongation of the multi-metal have achieve 524 MPa and 24.8 %, respectively.