Failure behavior analysis of oxide film formed on super-heater tubes of boiler during deep peak process

High-temperature components in the supercritical power plant experienced alternating thermal stresses under deep peak regulation, accelerating the cracking and spalling of the oxide film formed on the steam-side of super-heaters and re-heaters. This study employed the corrosion testing and finite element simulations to investigate the failure behavior of oxide films on super-heaters made by heat-resistant steelsT91 and austenitic HR3C during deep peak conditions. The experimental results indicate that the oxide film on T91was a double layer film containing Fe3O4 and Fe-Cr oxides, which was much thicker than that on HR3C. The spalling of the outer oxide film on T91 was more severe than that of HR3C. The analysis of thermal stress-strain under various loads and oxide film thicknesses revealed the significant shear stress between Fe3O4 and Fe-Cr within the oxide film on T91 steel. The significant shear stress caused the bigger strain within the oxide film on T91 steel, causing the spalling of the oxide film. Compared to the strain within the oxide film on T91 steel, the stress-strain within Cr2O3 oxide film on HR3C steel was notably lower than that on T91 steel. The failure behaviors of the oxide film on T91 and HR3C were quantitatively explained through experimental result and stress-strain simulation with the oxide film. The failure models of the oxide film on investigated steels were put forward. [Display omitted] •Failure analysis of the oxide film formed on boiler tubes during the deep peak process.•Corrosion and spalling of oxide film on T91 more severe than that of HR3C.•Thermal stress and strain within Cr2O3 film lower than that within Fe3O4 film.•Fluctuating thermal stress and strain promote cracking and spalling of oxide films.