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Abstract During the water pressure test of the waste heat boiler of the heavy metal recovery unit, many leaks were found in the superheater tube bundle. These leaks were all concentrated at the simmering bend location of the superheater tube parent material. This prompted an investigation into the causes of cracks in the superheater tubes of the waste heat boiler. The study followed a systematic approach, starting with macroscopic examination of the samples, nondestructive radiography, water quality examination, chemical composition analysis, metallographic analysis, scanning electron microscopy analysis, and energy dispersive spectroscopy (EDS). The results of these analyses revealed that the cracks were expanding from the inner wall to the outer wall, the cracks were dendritic in distribution, and the inner and tip of the cracks were full of grey-white oxides, with typical stress corrosion cracking characteristics. The water quality detected a pH value of 10.7, which was alkaline. This sequence of events ultimately led to the conclusion that the tubes were subjected to alkaline stress corrosion cracking due to the concentration of stresses at the simmering bends, which led to the leakage.
Lu et al. (Sun,) studied this question.