Atmospheric Stress Corrosion Crack Growth Rate Analyses of Austenitic Stainless Steel

摘要

Chloride induced stress corrosion cracking (CISCC) is a significant problem that can lead to premature failure of components in service. CISCC can occur when airborne salts deposit and deliquesce on component surfaces. The deliquescence of these salts in a humid environment creates a chloride-rich brine. The presence of this brine coupled with residual tensile stress could lead to CISCC. Although considerable work demonstrates conditions where CISCC can initiate, scarce information exists 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 a few research laboratories. The objective of the work described in this paper was to further the understanding of atmospheric CGR of stainless steel in a chloride-rich environment. Simulated sea salt was deposited on the surface of a stainless steel crack-growth specimen, which was exposed to varying relative humidity (RH) to understand how CGR changes in a given atmospheric environment. Results indicate that the SCC CGR of Type 304L stainless steel (UNS S30403) is dependent not only on the RH value, but also upon the RH rate of change with time, which has not been observed previously. This paper examines preliminary testing that elucidates some interesting features about the CGR of austenitic stainless steel under an atmospheric exposure.