Diffusion Bonding

Diffusion bonding is a method of joining metals similar to welding, but relies only on the surfaces diffusing into one another as a means of 'welding'. This process is aided by high pressure and/or temperature. Diffusion bonding has found several applications, one of which is welding materials which need to be kept out of the atmosphere, hence in a vacuum. This happens often in the weapons industry. A technique has been developed where a thin film of silver (on the order of microns) is placed between the surfaces to be bonded, and then temperature is raised near silver's melting point to facilitate diffusion. Advantages of this process over traditional welding include the small amount of bonding material needed and the fact that it is a very 'clean' process; it does not generate a lot of particulate matter.

Click here for more info