Fatigue Damage of Waterwall Tubes in a 1000 MW USC Boiler

Today’s coal-fired power plants in China are tasked with flexible operations, pushing for maximum output during peak price periods, and transitioning to low-load and multi-shift operation. These practices can accelerate material fatigue damage in major power plants components. Tubes in such applications are vulnerable to temperature and stress fluctuations, as a consequence the material may enter the fatigue regime, and fatigue cracks and fracture may subsequently occur with serious consequences. In this article, the failure of waterwall tubes in a supercritical boiler was analyzed, a full investigation into the failure cause was carried out involving in visual examination, optical microscope, mechanical test and phase analysis. The results show that the failure occurred due to thermal fatigue caused by temperature change. And recommendations are offered to help avoid similar failures in the future.