摘要
A series of heat treatments were performed to study the sensitization effect on the stress corrosion cracking (SCC) behavior of INCONEL 600 alloy. The microstructural evolution and the chromium depletion near the grain boundary were carefully studied using analytical electron microscopy (AEM). Comparable constant load tests in the solution containing various concentrations of sodium thiosulfate (Na 2 S 2 O 3 ) were, also performed in order to characterize the critical chromium concentration under the test conditions. It is observed that thermal treatment has a great effect on the microstructure and the chromium depletion profile of this alloy. Most specimens contained precipitates which were formed along grain boundaries in the semicontinuous form and were identified as M 7 C 3 with a hexagonal crystal structure (a 0 =1.398 nm, C 0 =0.45 nm). Some intragranular precipitates which were identified as M 23 C 6 with an fec crystal structure (a 0 =1.06 nm) were observed in the specimens aged for a longer period of time. The results of the constant load test showed that the susceptibility to SCC is sensitive to the chromium concentration at the grain boundary, and the minimum value to prevent SCC failure, under the test conditions, is approximately 8 wt pct. © 1989 The Minerals, Metals & Materials Society and ASM International.