DOI: 10.1515/pm-2026-0066 ISSN: 2195-8599
Analysis of the causes of cracking in the squirrel cage bar of a gas turbine
S. Qu, H. Zhang, L. Liu, C. Dong, Z. Zhang, H. Yu, N. XuAbstract
After a 1100 h bench test, surface cracking was detected in multiple bars of the squirrel cage. Macro- and microscopic inspections revealed that the cracks were confined to the nitriding layer, which exhibited mixed fracture characteristics dominated by intergranular fracture, together with high hardness and elevated hydrogen content. The distribution and morphology of the cracks indicate that the bars experienced elastic bending deformation, resulting in hydrogen-induced cracking due to deformation incompatibility between the nitriding layer and the matrix. Based on these crack characteristics, the abnormal instantaneous load generated by the rubbing between the seventh-stage blades and the casing should be the cause of the cracks.