Nanocrystalline Surface Layer on AISI 52100 Steel Induced by Supersonic Fine Particles Bombarding

Surface treatment of AISI 52100 steel by supersonic fine particles bombarding (SFPB) was studied in this article. The surface topography, morphology of the surface layer, and microhardness distribution of the surface layer have been investigated using a surface profiler system, a scanning electron microscopy (SEM), and a microvickers hardness tester. The microstructure, phase composition, and residual stress distribution of the surface layer in AISI 52100 steel after the SFBP treatment have been characterized by means of x-ray diffraction, SEM, and transmission electron microscopy. The results showed that a nanocrystalline surface (NS) layer was formed on the top surface of the SFBP-treated AISI 52100 steel samples. The NS layer is about 2 mu m in thickness with a surface roughness of R (a) = 1.2 mu m, R (y) = 6.7 mu m, R (z) = 6.0 mu m. Phase transitions occurred in the surface of the SFBP-treated samples. Residual compressive stress is obtained at the surface of the SFBP-treated samples. The maximum value of compressive stress appears at the outermost of the surface, and the affection region of the whole surface is about 60 mu m in thickness. A hardened surface layer has been fabricated in the AISI 52100 steel. The thickness of the hardened surface layer is about 70 mu m. The maximum value of hardness occurs at the depth of 20 mu m from the outermost surface.