Atmospheric stress corrosion crack growth rate analyses of austenitic stainless steel

摘要

Chloride induced stress corrosion cracking (CISCC) is a significant problem that has been observed to lead to premature failure of components at various facilities. CISCC can occur when airborne salts deposit and accumulate on the outer surface of components. Deliquescence of these salts in a humid environment could create a chloride-rich brine. This, along with a residual tensile stress, could lead to CISCC. There has been much work demonstrating conditions where CISCC can initiate, but there is very little information on the actual SCC crack growth rate (CGR) under an atmospheric environment. The limited amount of atmospheric SCC CGR measurements have been obtained either from operating experience or by a few labs. However, the laboratory tests were from samples where the loading conditions are not easily controlled. The objective of the work described in this paper was to conduct atmospheric CGR tests under controlled loading conditions. An atmospheric chamber was assembled around a loading frame that could control both the chamber relative humidity (RH) and temperature. Results indicate that the SCC CGR of 304L stainless steel is dependent not only on the RH value, but is also dependent upon the RH rate of change with time, which has not been observed previously. This paper examines some preliminary tests that elucidate some interesting features about the CGR of austenitic steel under an atmospheric exposure.