Cause Analysis of Tube Burst of 15CrMo Steel Superheater Tube

Tube burst of the superheater tube of a power plant boiler caused the unplanned shutdown of the entire unit.The causes of superheater tube burst were analyzed by macroscopical examination,chemical composition analysis,metallographic examination,tube wall morphology analysis,hardness test,bulge volume calculation and so on.The results show that the superheater tube burst had the characteristics of long-term overheating.The superheater tube was overheated for a long time due to the over-load operation of the boiler and oxidation layer,which resulted in the deterioration of the tube structure,the appearance of creep holes and microcracks,which led to the decrease of the superheater tube strength and eventually the tube burst.The failure mode of superheater tube was high temperature creep cracking caused by long-term overheating.