Failure analysis on 12cr1mov steel tube of high temperature reheater for 600 mw subcritical boiler

A 600 MW subcritical boiler high temperature reheater tube of 12Cr1MoV steel leaks after running for 11×10⁴ h. Failure Analysis of the high temperature reheater is studied by optical microscope (OM), scanning electron microscopy(SEM) and energy dispersive spectroscopy(EDS), etc. The results show that under long-term service at high temperature, the alloy elements have been depleted in the matrix. The oxidation layer of the inner wall is too thick, and the micro-structure is degraded obviously. Many creep cavities and micro-cracks appear in the fire-facing side of the elbow. The micro-cracks extending along the grain boundaries are filled with oxide. In conclusion, the degradation of the microstructure caused by long term overheat is the main reason for the failure of 12Cr1MoV reheater tube, and the creep cracking causes the leak.