Cause Analysis on Tube Burst of Superheater Tube of T91 Steel in Supercritical Boiler

The platen superheater tube of a domestic flame boiler burst and leaked after one month operation. The burst causes of superheater tube were analyzed by means of macroscopic examination, chemical composition analysis, hardness test, metallographic examination, scanning electron microscope and energy spectrum analysis. The results show that long-time over temperature operation caused tube burst. Weld beadings inside the girth weld of superheater tube joint blocked the steam flow, and oxide skin impacted heat transfer, which caused partial wall overheating for a long time. Serious aging of microstructure and obvious creep damage of burst mouth reduced the strength of tube material, and the pressure bearing capacity of tube wall and finally led to burst and leakage of superheater tube.