Effect of Grain Boundary Microchemistry on IGSCC of Alloy 132 in a Simulated BWR Environment

Abstract:

The effects of cold working and heat treatment on caustic stress corrosion cracking (SCC) of mill annealed (MA) alloy 800M in boiling solution of 50%NaOH+0.3%SiO2+0.3%Na2S2O3 were investigated by means of microstructure examination, tensile test, X-ray stress analysis, SCC testing of C-rings, Auger electron spectroscopy (AES), scanning electron microscopy (SEM) and metallography. The microstructure of alloy 800M under tested conditions was austenite. With a strain of 25% by cold working, the grains of alloy 800M became longer, yield strength (YS) and ultimate tensile strength (UTS) increased, elongation (δ ) decreased, residual stress and the susceptibility to SCC increased. With increasing temperature of heat treatment of alloy 800M with cold working, the grains became bigger , residual stress, YS and UTS decreased and δ increased, the susceptibility to SCC of alloy 800M decreased. In boiling caustic solution, SCC cracks on the surfaces of C-ring specimens polarized potentiostatically at –20mV/SCE initiated from pitting and propagated along grain boundaries. AES analysis indicated that the surface films on MA alloy 800M were enriched in nickel and depleted in iron and chromium.

• Periodical: Key Engineering Materials (Volumes 297-300)
• Pages: 986-992
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.297-300.986
• Online since: November 2005
• Authors: Yo-ichi Takeda, Hiroyuki Yamauchi, Qunjia Peng, Tetsuo Shoji
• Keywords: Auger Electron Spectroscopy (AES), Grain Boundary Microchemistry, Intergranular Stress Corrosion Cracking

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