Effect of deposition sequence on interface characteristics of IN718/CuSn10 horizontal bimetallic structures via laser directed energy deposition

Abstract

In this study, horizontally connected IN718/CuSn10 bimetallic structures with different deposition sequences were fabricated by laser directed energy deposition (LDED). The interfacial characteristics and defect formation mechanisms under different deposition sequences were investigated. When IN718 was deposited first, followed by CuSn10 alloy deposited(NiA-CuA sequence), the bimetallic structure obtains excellent interfacial bonding properties. This structure demonstrated an ultimate tensile strength of 566 MPa, a value that falls between the tensile strengths of the IN718 and the CuSn10 alloys. For the NiA-CuA bimetallic structure, the remelted IN718 alloy was introduced into the CuSn10 deposited layer, the preferential precipitation of the Fe/Cr element induces the formation of equiaxed grains. The presence of a minimal quantity of copper (Cu) diffused into the IN718 alloy does not result in the occurrence of copper segregation within the dendrites. This phenomenon serves to mitigate the risk of intergranular cracking. In contrast, when CuSn10 was deposited first followed by IN718 alloy deposited (CuA-NiA sequence), the remelting process introduces a higher amount of Cu alloy into the first track of IN718, which results in a large amount of Cu segregation in the dendrites, leading to a higher cracking susceptibility of the first track of the deposited IN718 layer. Furthermore, the higher Cu content in the first-track IN718 alloy leads to a significant composition gradient at the interface during the subsequent deposition of the second track of IN718, and its large thermal conductivity and thermal expansion coefficient differences make it highly susceptible to cracking under thermal stresses. This research provides an experimental basis for designing and regulating the interface of Ni/Cu bimetallic structures.

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