Multi-material additive-manufacturing of tungsten - copper alloy bimetallic structure with a stainless-steel interlayer and associated bonding mechanisms

Abstract

Copper alloy–tungsten (CuA-W) material combination offers high-temperature damage resistance and excellent plasma radiation resistance. At present, there is a lack of knowledge on laser-based powder bed fusion (LPBF) additive manufacturing of CuA-W bimetallic structures. Here we show the influence of the build strategies (including directly bonding, using CuA-W powder mixture, and using the stainless steel (SS) interlayer) on the bonding of CuA to W. The experimental results show that pure CuA became spherical on the surface of solid W. The powder layers composed of the CuA-W mixture are thermally deformed after printing several layers. Using a SS transition layer between CuA and W, good bonding between the materials is achieved due to solid-state diffusion and grain boundary diffusion. We have also found that if the melting points of the two materials are significantly different, the printing of the high melting point material first will most likely make the material interface unmelted in multi-material LPBF. The material combination must have good wettability and a high element solid-state diffusion coefficient to achieve good bonding in such a condition. This study would be helpful for future investigation on multi-material AM involving a metallic material combination with significant difference in their melting points.