Subsurface microstructural degeneration of Super304H boiler tube under the synergy of fireside corrosion and creep stress

The deterioration mechanism of creep rupture life of Super304H in a lab simulated fireside corrosion environment at 650 °C is investigated. This includes in-depth study of microstructural evolution in grain structure, elemental distribution and precipitates. Results reveal a two-thirds reduction in creep life by corrosive media. The major reason for this degradation under the synergy of high-temperature corrosion and creep stress is considered to be more serious dynamic recrystallization and martensitic transformation occurring in the surface layer. The fractography of the rupture specimens indicates creep voids coarsening is responsible for fracture in both conditions.