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.

The Laves phase formed during the long-term creep of 9% Cr heat-resistant steels plays an important role in their high-temperature mechanical properties. Detecting and quantifying the Laves phase is one of the main problems in predicting the creep residual life. This study detects and quantifies the Laves phase in various 9% Cr heat-resistant steel samples by anodic polarization. Both T92/P92 samples after creep and 9Cr ferritic martensitic samples after thermal ageing precipitate Laves phase particles, and the content of the Laves phase increases with the service time. Comparing the results obtained by the electrochemical method with those obtained by the traditional SEM observation method, it can be found that there is a similar two-stage linear relationship between the two results in all materials, which is related to the diameter change of Laves phase particles during service. According to the correlation between the Laves phase content and creep time, an extrapolation method for the prediction of the residual creep life is proposed. The results show that the creep life of P92 can be predicted by using the dissolved charge density of the Laves phase with high prediction accuracy. This method has the potential to evaluate the service states of materials and predict the long-term creep life in the industrial field.