I - CSC des alliages de nickel dans l’eau à haute température. Discrimination entre les différents mécanismes

Stress corrosion cracking of nickel base alloys in high temperature water discrimination between different mechanisms

Abstract

The aim of the present study is to progress toward understanding the stress corrosion cracking mechanism of Alloy 600 in high-temperature water (Alloy 600 is the constitutive material of steam generators tubing in pressurized water reactors). It consists in determining which is the mechanism the most likely to occur among all mechanisms proposed in different models. The search of the rate limiting step is carried out by means of calculations which consist in theoretically evaluating the rate of some steps and comparing it with the measured crack growth rate. The analysis of models given in literature suggests that a mechanism involving the formation of a new phase within the material can be invoked to explain the cracking phenomenon. Then, specific tests are performed to test this hypothesis. Others experiments are conducted to study the exact role of hydrogen on the process. The first results are presented here.