Failure of 2.25Cr-1Mo steel superheater tubes in a fluidized bed combustor due to fireside corrosion

►Failure analysis of superheater tubes of 2.25Cr-1Mo steel used in a circulating fluidized bed combustion boiler has been carried out. ►Spherodization in the material have been shown to relate to the operating temperature and explained. ►The inner oxide, the outer oxide and the deposits on outer surface on the superheater tube have been shown and characterized compositionally. ►Oxide penetrating into the base metal is characterized by elemental area scans. ►Typical signatures of creep in the material have been shown to conclude that the final failure was due to creep.