Microstructure evolution and oxidation behaviour of shot-peened S30432 stainless steel during exposure in double reheat USC power plant steam environment

ABSTRACT

The microstructural evolution and oxidation behaviour of shot-peened S30432 stainless steel during exposure in steam environment in a real double reheat USC power plant has been investigated through microstructural characterisation using electron microscopes. The results indicated that shot-peening treatment introduced a thick deformation layer to the material, and this deformation layer consisted of an outer nanostructured layer and an inner layer with deformation bands. During thermal exposure, the nanostructured layer experienced extensive recrystallisation and coarsening, and numerous σ particles were found to precipitate in the deformation layer as well. Furthermore, a double layer structured oxide formed on the material, and the oxide layer grew slowly after exposure for 6219 h, which was related to the formation of a thin and dense SiO₂ layer at the metal/oxide interface. The mechanism of the microstructural evolution and oxidation has been discussed.

KEYWORDS:

• S30432 stainless steel
• shot peening
• supercritical double reheat
• microstructure
• oxide scale

Acknowledgments

The authors gratefully acknowledge financial support from the Science and Technology Project of China Huaneng Group [grant number HNKJ15-H03] and National Nature Science Foundation of China [grant number 51501130]. Dr Litao Chang from the University of Manchester is acknowledged for beneficial discussions.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Science and Technology Project of China Huaneng Group [HNKJ15-H03] and National Natural Science Foundation of China [51501130].