Diffusion welding through vacuum-deposited porous interlayers

Results of studying the processes of diffusion welding of similar (steel) and dissimilar (steel and bonze) materials through interlayers in the form of thin foil of porous nickel and copper are considered. Thin foils of porous structure were produced by vapour phase condensation on the substrate in electron beam evaporation of elements in vacuum. Application of such foils as interlayers not only promotes formation of defect-free joints, but also leads to lowering of temperature and pressure of diffusion welding, compared to welding without an interlayer. Correlation of the change of parameters of diffusion welding through porous foil and lowering of the temperature of its transition into the superplastic state that is accompanied by the change of characteristics of foil porous structure, suggested that the processes running in the interlayer may promote establishment of physical contact between the surfaces being welded and accelerate the diffusion processes in the joint zone.