Effect of Residual Stress and Microstructures on 316 Stainless Steel Treated by LSP

Abstract

In order to improve the stress corrosion resistance of 316 stainless steel, a new technology was proposed and studied. The 316 stainless steel sample was treated by laser shock processing (LSP). The residual stress and microstructures of 316 stainless steel with and without LSP were measured and compared by the methods of X-ray, transmission electron microscopy (TEM) and Electron Back-ScatteredDiffraction (EBSD), and the strengthening mechanism was discussed. It showed that the high residual compressive stress introduced by laser shock processing was about-112 MPa. The TEM and EBSD results showed that severe plastic deformation and nanocrystals layer were formed by LSP, and the orientation of the grains had evident rotation in the process of plastic deformation. These helped to enhance the stress corrosion resistance of 316 stainless steel.

Metastable pitting behaviour of austenite stainless steel under compressive residual stress

“…It is noteworthy that there is a strong symbiotic relationship between compressive residual stress and changes in the microstructure and/or surface chemical composition. For example, besides the compressive residual stress, both high density dislocations and grain refinements were induced by LSP in the SS sample surface . Additionally, strain‐induced martensite can be introduced after deformation in certain cases.…”

“…For example, besides the compressive residual stress, both high density dislocations and grain refinements were induced by LSP in the SS sample surface. [8] Additionally, strain-induced martensite can be introduced after deformation [9][10][11] in certain cases. The variation of surface modifications has been proven to be closely related to the initiation, propagation and repassivation of a metastable pit.…”