Understanding in the failure of the tubes in a power boiler in order to set up the appropriate countermeasures is of great importance. This paper described the failure examination of the thermally failed SA210 Gr. C steel used in the superheat zone in a coal-fired power plant. The investigation dealed with visual inspection, microstructure studies and chemical analysis. Results indicated that the main failure of this tube was related to the prolonged overheating. The formation of the thick layer on the failed tube favored the prolonged overheating, resulting in the thermally degraded microstructure known as “graphitization” and eventually led to the stress rupture of this tube. It is then suggested to employ the low alloy steel alloyed with chromium and molybdenum. The scale removal during the inspection period is also recommended.