AWS WHC-3.12:2008

Diffusion Welding and Diffusion Brazing
Scope : Both diffusion welding (DFW) and diffusion brazing (DFB) are diffusion-controlled joining processes, but the former is a solid-state process while the latter involves a liquid phase in the process. Diffusion welding produces a weld by the application of pressure at elevated temperature with no macroscopic deformation or relative motion of the workpieces. A filler metal may be inserted between the faying surfaces. A variation of diffusion welding, hot isostatic pressure welding (HIPW) produces coalescence by heating the metals and applying hot inert gas under pressure.1, 2 Diffusion brazing is distinguished from diffusion welding by the fact that liquid braze filler metal is introduced at the joint interface. When liquid filler metal is used, only moderate-to-low pressures are necessary versus the high pressures used for diffusion welding. The similarities and common features of diffusion welding and diffusion brazing are discussed in general in the first sections of this chapter. Information specific to each process is presented in separate welding and brazing sections. Both processes are discussed in the sections on Quality and Inspection, Economics, and Safe Practices. A brief section on a related process, diffusion soldering, also is included.