A case study on failure of superheater tubes in an industrial power plant

A failure analysis investigation was carried out on the secondary Superheater tubes of a boiler unit in a steam power plant. The tubes, made of DIN-16CrMo4 steel, failed by bulging and rupture only after about three years of operation. Metallurgical investigations revealed that microstructural degradation had mainly occurred at the external (fireside) tube surface. Long-term overheating was identified as the root cause of the premature failure.