The microstructural refinement of cobalt based alloy (Stellite NO. 6) by laser cladding and friction stir processing (FSP) was studied. A nanometer-sized microstructure consisting of fine carbide (particle size: 100∼200 nm) and a grain (grain size: 150∼250 nm) was successfully fabricated by the FSP on the laser clad cobalt based alloy. The nanostructured cobalt based alloy (Stellite NO. 6) had an extremely high hardness of about 750 HV.
