Microstructural Characterization of Austenitic Stainless Steels Nitrided Layers by EBSD

MARTINA AVALOS; BRUHL, SONIA; SIMISON, SILVIA; BOLMARO, RAÚL E.

Cancún

Congreso; XXIV International Materials Research Congress; 2015

Sociedad Mexicana de Materiales

The introduction of nitrogen by different techniques in the surface of steels is a well known process to develop a hard layer with excellent wear resistance. The main drawback of this process is the loss of corrosion resistance, what is particularly problematic in stainless steels. In the last years the nitrogen incorporation under selected condition in austenitic stainless steels has been developed. The process results in the development of a hard layer with excellent wear and corrosion properties, but the mechanisms involved in this process are not well understood yet. In this study, samples of AISI 316 fcc steel with similar surface nitrogen content introduced by Direct Current Plasma nitriding (DC), Plasma Immersion Ion Implantation (PI3) and Low Energy Ion implantation (LEI) were characterized by Electron Backscatter Diffraction EBSD + Energy Dispersion Spectroscopy (EDS) coupled to a Scanning Electron Microscope (SEM). The effect of the nitriding methodology in the microstructure is the purpose of the current research. Despite the main objective of nitriding process is to obtain a hard layer, the concurrent microstructure development conditioned the mechanical and corrosion responses. In this work the focus is on the lattice reorientation resulting for nitriding and the microstructural defects developed in the nitride layer as a consequence of plastic deformation. The expansion of the lattice due to nitrogen diffusion induce plasticity because of constrains imposed by other nitrided grains and probably by the non-nitrided region acting as a rigid substrate. From this microstructural information the mechanism of nitrogen introduction and hardening are discussed.