Stress corrosion cracking initiation of alloy 82 in hydrogenated steam

Abstract

Experiments in hydrogenated steam were performed on several U-bend specimens extracted from two Alloy 82 welds. Results demonstrated that Alloy 82 is susceptible to SCC in hydrogenated steam at 400 °C and its susceptibility depends on its chemical composition, welding process and thermal treatment. The microstructure was characterized in the apex of the U-bend specimens. Chemical analysis were performed by electron probe microanalyser (EPMA) and secondary ion mass spectrometry (SIMS) on several areas in the weld in order to correlate crack initiation with chemical heterogeneities. It was concluded that there are more cracks in the roots of the weld passes where the impurity content (sulfur, titanium and aluminum) is higher.