Abstract
The frictional stir burnishing can give frictional heat and large stir, to the surface of work pieces. Those factors made enhanced layers on some of steel materials (S45C and SUS304). The enhanced layers are observed clearly in cross section of processing surface by optical microscope in those cases. S45C carbon-steel was hardened and its hardness is over 900HV. It is thought that the main factor that the hardened layer was obtained is martensitic transformation. SUS304 stainless-steel which can be not given heat-treatment for transformation was also hardened. It is thought that the factors that the hardened layers were obtained is grain refinement or deformation induced transformation.
