Mechanical Properties of TiN Coating on Nanocrystalline Surface Layer of 304 Stainless Steel

Surface nanocrystallization (SNC) can markedly improve surface mechanical properties of metallic materials and accelerate thermal diffusion of elemental atoms. In this work we study the effects of SNC on structure and mechanical properties of TiN coating on 304 stainless steel substrate. The steel was subjected to 15 min surface mechanical attrition treatment (SMAT) to obtain a nanocrystalline surface layer with thickness about 30 mu m. TiN coating was deposited on the surface nanocrystallized and the coarse-grained steel substrates by multi-arc ion plating. X-ray diffraction shows that TiN(111) orientation of the coating is much reduced due to SNC treatment. Mechanical tests show that the nanocrystalline surface layer has obviously increased surface hardness of the coating system; toughness and adhesion of the coating, impact resistance of the coating system are also improved. Advantages of SNC-hard coating processing over the conventional duplex treatment consisting of thermal diffusion process-hard coating are shortly discussed.