IMPROVEMENT OF STRESS CORROSION CRACKING (SCC) RESISTANCE BY CYCLIC PRE-STRAINING IN 316L AUSTENITIC STAINLESS STEEL IN BOILING MGCL{sub}2 SOLUTION - IMPORTANCE OF THE PRE-DEFORMATION MODE

摘要

Improving the materials resistance to SCC has become a topic of wide interest for theoretical, engineering and financial reasons. The aim of this paper is to propose a process to delay the SCC damage. Recent studies of 316L austenitic stainless steel in boiling MgCl2 solutions show an improvement in SCC resistance by cyclic pre-straining in low cycle fatigue [1]. This improvement consists of an increase in both crack initiation strain and strain to failure, during Slow Strain Rate Tensile (SSRT) tests in aqueous solution. This paper analyses the effect of pre-fatigue in 316L on its mechanical and electrochemical response to better understand the delay of SCC damage in boiling MgCl{sub}2. The explanation for this beneficial effect is related to a modification of both surface electrochemical reactions kinetics and corrosion/plasticity interactions at the crack tip, due to the particular fatigue dislocation structure.