TTT media, page-1218

It's called friction stir welding

There is a fairly decent article on it by TWI one of TTTs customers

What Is Friction Stir Processing? (A Complete Guide) - TWI (twi-global.com)

the problem with friction stir is that you need to be able to apply extreme localised pressure to 'weld' the part.
Essentially a tool applies a spinning force under such high pressure that it mixes the grains of the metal together in a whirlpool like fashion without necessarily heating the metal to the point it changes state from solid to liquid, it just acts like a liquid under the pressure

Whilst there might be some competition in some verticals, by the looks of the friction stir technology you need a flat surface in order to properly apply the pressure. You also wouldn't want to use this technique to repair parts which are too significantly degraded or thin as it would just break the part, same goes for repairing parts that contain liquid and are not empty, or metal parts which encase electronics as you may damage or destroy whats inside.

Well atleast in my opinion anyway