Stress corrosion cracking and hydrogen-induced cracking of amorphous Fe 74.5Ni 10Si 3.5B 9C 2

Abstract

Stress corrosion cracking (SCC) in NaCl solution and hydrogen-induced cracking (HIC) during dynamic charging of Fe 74.5Ni 10Si 3.5B 9C 2 amorphous alloy were investigated through sustained load tests. The normalized threshold stress of SCC was σ SCC/ σ F=0.04, where σ F is fracture strength in air. Anodic polarization and addition of As 2O 3 into the solution did not change σ SCC/ σ F, but cathodic polarization increased σ SCC/ σ F from 0.04 to 0.31. Cathodic polarization increased but anodic polarization decreased the time to failure during SCC at the constant load of σ=0.27 σ F. The normalized threshold stress of HIC, σ HIC/ σ F, was linearly decreased with the increase in logarithm of hydrogen concentration ( C 0) and kept a minimum constant when C 0 was larger than a critical value, i.e., σ HIC/ σ F=1.58−0.36ln C 0 ( C 0⩽74.4 wppm) and 0.1 ( C 0⩾74.4 wppm). The threshold stress of HIC during dynamic charging with the maximum current was larger than that of SCC at open-circuit potential. Fracture surfaces of HIC were also different with that of SCC. Experiments indicated that SCC of the amorphous alloy in the NaCl solution is controlled by anodic dissolution process instead of hydrogen.