Evolution of the micro/nanostructureof high nitrogen stainless steels, related to the deformation mechanisms on the cavitation erosion resistance of stainless steels

Abstract

The aim of this project is to establish relationships between the micro and nanostructure, and the cavitation erosion resistance of stainless steels in two different stainless steels: an austenitic stainless steel and a high nitrogen, medium alloyed duplex stainless steel. These relationships will be determined through the study of the degradation and plastic strain mechanisms observed at the surface, in the micro and nano levels, during vibrational cavitation tests.The high nitrogen contents of the tested steels will be supplied by a high temperature gas nitriding treatment. Part of the gas-nitrided samples will be submitted to plastic strain by rolling to determine if there is a synergic between nitrogen content and work hardening, before and during cavitation erosion, and its relationship with the micro and nanostructure in each case.The microstructural characterization will be done using Transmission Electronic Microscopy TEM, Scanning Electron Microscopy SEM, Electron Backscatter Diffraction EBSD, Light Optical Microscopy LOM and X Ray Diffraction XRD. TEM analysis will be used to characterize dislocationarrays and to assess the Stacking-Fault Energy of the studied alloys, trying to establish relationships between crystal structure, chemical composition and operative deformation modes in the high nitrogen steels.