Solid-state diffusion welding (SD)
Diffusion bonding (welding or brazing)

Solid-phase bonding is based on diffusion and local viscoplastic deformation at interface asperities. Both mechanisms are activated by temperature and contact pressure:

• the temperature for diffusion bonding is generally between 0.6 and 0.9 T_f where T_f (in K) is the lower melting temperature of the two materials;

• the stress is between 0.2 and 0.9 times σ_e, the lower of the flow stresses of the two materials at joining temperature.

These conditions are reminiscent of those chosen for powder metallurgy. This is not surprising, since powder densification technology simultaneously assembles a very large number of particles. The variation in flow stresses (often equated with creep rupture stress in around 1,000 h) of iron-, nickel- or cobalt-based metal alloys as a function of temperature is shown in figure...