US Patent 8220693 Modified surfaces using friction stir processing

A procedure for incorporating particles to a predetermined depth in a body to develop a composite surface layer using friction stir processing is described. The process comprises; preparing the surface of the body; applying particulate matter to the prepared surface; selecting a friction stir tool with a pin length substantially equal to the desired composite layer thickness; using a friction stir process to frictionally heat, stir and intermix the particulate matter with the matrix of the article; and traversing the friction stir tool across the body.