Analysis of cracking failures in water-cooled wall fins and thermal peaking unit mitigation strategies

Abstract The causes of leakage in the submitted superheater tubes were analyzed using the analysis of macroscopic morphology, chemical composition, and metallography. The analysis results indicate that the chemical composition of the failed superheater tube is within the standard range, and the metallographic structure is ferrite + pearlite, with no abnormalities in the metallographic structure. The main reason for the failure of water-cooled wall tubes and superheater tubes may be the formation of fatigue cracks on the inner and outer walls of the superheater tubes under cyclic stress. As the two fatigue cracks grow and converge, penetrating cracks form, ultimately leading to the initial leakage of the superheater tubes. In addition, the excessive depth of the weld pool in the fins of the superheater tube is another crucial factor that promotes accelerated cracking of the superheater tube. It is recommended that power plants reasonably regulate the temperature difference fluctuation rate of boilers to prevent similar failure accidents from occurring.