US Patent 10092975 Solid state additive manufacturing system

A process for solid state deposition of a material onto a workpiece includes the steps of providing a rod of metallic deposition material, exerting pressure at one end of the rod to move the metallic deposition material into a deposition zone, rotating the rod while the pressure is being exerted to generate frictional heat when the rod contacts a surface of the workpiece, and raising the temperature of the metallic deposition material to reduce the amount of frictional heat which needs to be generated during the rotating step and to produce a microstructure which is substantially free of porosity and which has a fine grain size.