The Stress Corrosion Cracking Of 2.25 Cr--1 Mo Ferritic Steel In Caustic Environments

Author:  Hurst, P. and Cowen, H.C.
Source:  Nucl. Technol. 55, (2), Nov.'81
Doc ID:  1981094
Year of Publication:  1981
Abstract:  
Stress corrosion studies in caustic environments have been carried out on ferritic 2.25Cr--1Mo steel, with particular reference to its use in the evaporators of the U.K. prototype fast reactor. The quench-hardened steel has been found to be susceptible to stress corrosion cracking (SCC) throughout the temp. range of 50 to 300 deg C. In 30% caustic soda at 116 deg C, this susceptibility extends over the potential range --900 to +100 mV (Hg/Hg0). On tempering, SCC occurs at --900 to --700 mV, but only at more positive potentials when preceded by an overheating treatment. Mechanisms by which cracking occurs under the different conditions studied are discussed. Cracking can occur in hard tube-to-tube-plate welds exposed to caustic environments as a consequence of fabrication stresses, but it has been shown that this can be avoided by shot peening. Descriptors: Chromium molybdenum steels-- Corrosion; Nuclear reactor components-- Corrosion; Boiler tubes-- Corrosion; Stress corrosion cracking; Sodium hydroxide-- Environment; Tempering; Shot peening