Impact of Fireside Corrosion on the Creep Rupture Life and Oxide Scale Structure of a Super304H Boiler Tube

The creep rupture life of commercial Super304H in fireside corrosion (coal ash and flue gas) and static air environment at 650 degrees C was investigated. Results showed that the creep rupture life under fireside corrosion conditions decreases by 26.5% to 83.3% at different stress levels, compared with that in air. The corrosion products, including their composition, morphology, and distribution, and the microstructure of substrate were characterized to research the impact of the fireside corrosion on the creep rupture life. The exfoliation of oxide scales and serious surface cracking resulted from fireside corrosion were detrimental for the creep properties of the alloy. The formation of internal sulfides promoted the initiation and propagation of intergranular cracks in the substrate during creep tests. These degradations of Super304H in fireside corrosion contributed to premature creep rupture.