Refractory metals low temperature diffusion bonding

In this dissertation, the minimization of the diffusion bonding temperature during refractory metals’ diffusion bonding process was studied. Two pure refractory metals were used in this study: molybdenum and tungsten. The influence on the joint quality of molybdenum structural conditions, as well as molybdenum surface conditions, was examined. Moreover, diffusion bonding of tungsten to Oxygen Free Electrical copper and copper alloy (CuCr1Zr), without using an interlayer but instead using different bonding parameters, was evaluated. Diffusion bonding of tungsten to Oxygen Free Electrical copper and to CuCr1Zr alloy using titanium and nickel together as intermediate layers was also investigated, as well as the diffusion bonding of tungsten to Oxygen Free Electrical copper and to CuCr1Zr alloy using only nickel as an intermediate layer. The resulting joints were evaluated using optical microscopy, SEM, hardness, shear, and tensile tests. The residual stresses, as well as the deformation, that are generated due to the diffusion bonding process were evaluated through a FEM simulation using the software ANSYS.
For pure molybdenum joints, successful results in minimizing bonding temperature were obtained. In tungsten to Oxygen Free Electrical copper and to CuCr1Zr alloy joints contrasting results were achieved.