Butt diffusion bonding

In diffusion welding, you join two metal parts under heat and pressure in a vacuum or shielding gas. The parts must be clean and flat; the faying surfaces then press together on an atomic level – there is no melt, the joint forms purely by diffusion. The parameters (temperature, pressure, time) depend heavily on the material, so you need to follow the datasheet or use experience values. If the surfaces are not clean or the pressure is too low, you get porosity and no sound weld. This process is typical for joining dissimilar metals or when you want a low-stress, distortion-free joint.