Effects of Deposition Strategies on Microstructure and Mechanical Properties of 316L Stainless Steel and Inconel 625 Alloy Dissimilar Structure Fabricated by Cold Metal Transfer Arc Additive Manufacturing

In this study, dissimilar structures of 316L and Inconel 625 were fabricated using wire and arc additive manufacturing with the cold metal transfer plus pulse mode (CMT+P). Based on various arc scanning strategies, including single-layer and multi-layer deposition, in vertical and horizontal building directions, the evolution of interface microstructure and mechanical properties of additively manufactured heterogeneous structures were studied. The microstructure analysis showed that during single-layer deposition, both 316L and Inconel 625 formed dendrites and columnar crystals. During the multi-layer deposition process, the 316L material solidified to form a dual-phase microstructure consisting of austenite and ferrite, whereas the Inconel 625 primarily formed an austenite microstructure. The segregation of elements such as Nb and Mo occurred at the interface, resulting in the formation of numerous precipitated phases at the grain boundary. At the interface of the vertically deposited sample, the inadequate diffusion of elements resulted in the formation of a transition layer in the microstructure. The microhardness of the deposited Inconel 625 layer was approximately 215 HV, while the microhardness of the deposited 316L layer ranged from 170 to 200 HV. The tensile strength and elongation rate of the horizontally deposited samples were higher than those of the vertically deposited structure. Both the tensile strength and elongation rate of the multilayer deposited structure were reduced due to the presence of numerous interfaces. The maximum tensile strength and elongation rate of horizontal single-layer samples were 488.57 MPa and 43.53%, respectively. The average tensile strength and elongation of vertical multi-layer samples were 387.26 MPa and 17.79%, respectively. Results showed that the mechanical properties of the SS316L/Inconel 625 heterogeneous structure in wire and arc additive manufacturing are clearly influenced by the deposition strategies and interface orientation.