Nanoparticle-strengthened-martensitic Surface Layered Constructed Steel by Plasma Hardening Rout

A comprehensive study was carried out on the strain-induced martensitic transformation, its reversion to austenite, the resultant grain refinement, and the enhancement of strength and strain-hardening ability through the transformation-induced plasticity (TRIP) effect in a commercial stainless steel with emphasis on the mechanisms and the microstructural evolution. It is shown that depending on the cooling rate and temperature conditions of austenite decomposition, pearlitic and martensitic transformations proceed with the formation of gradient-layered structure, modernization of steel surface layer structure is obtained while the chemical composition, structure and the central layer properties of the processed product remain unchanged. The non-diffusive martensitic transformation is developed in the surface zone that makes the formation of needle martensite. In the underlying layers, the decomposition of austenite proceeds by diffusion and is followed by the formation of a lamellar ferrite-carbide mixture of different degrees of dispersion. It is noted that the formation in the surface layer of plasma-strengthened steel of the gradient-layered structure allows to exclude the formation of a sharp transition from martensite structures to trostite-martensite and mixed lamellar structures, which is a concentrator of internal residual stresses.