Friction surfacing (FS) was first patented in the 40´s and is now well established as a solid
state technology to produce metallic coatings. While FSP modifies the microstructure of a
surface by simply deforming, recrystallize and homogenise the grain structure, FS modifies
its chemistry. In friction surfacing a consumable rod under rotation is pressed under an
axial load against the surface as depicted in Fig. 9. Heat generated in the initial friction
contact promotes viscoplastic deformation at the tip of the rod. As the consumable travels
along the substrate, the viscoplastic material at the vicinity of the rubbing interface flows
into flash or is transferred over onto the substrate surface, while pressure and heat
conditions triggers an inter diffusion process that soundly bonds the deposit. As the
material undergoes a thermo-mechanical process, a fine grain microstructure is also
produced by dynamic recrystallization.