Interaction of 16Kh12MVSFBR Steel with Nitrogen at 650–800°C

Abstract—The corrosion behavior of 16Kh12MVSFBR steel during high-temperature nitrogen treatment has been studied. The surface composition and structure of the steel are shown to change. Interactions between the electronegative alloying elements of the ferritic–martensitic steel (Mn, Cr) and the gas phase components (nitrogen, impurity oxygen) occur on the material surface. The formation of chromium and manganese nitrides and oxides of various stoichiometric compositions is detected. The corrosion rates of 16Kh12MVSFBR steel at temperatures of 650 and 800°C are 0.104 and 0.241 mm/year after holding for 12 h and 0.013 and 0.020 mm/year after holding for 84 h, respectively. The character of surface degradation of steel samples is continuous nonuniform, with clear localization of corrosion at grain boundaries in steel, which is associated with the formation of secondary phases along the grain boundaries. Conclusions are drawn regarding changes in the structure during high-temperature holding and the character of corrosion damage. Based on the results of thermodynamic modeling and X-ray fluorescence analysis, conclusions are made about the composition of the corrosion products of 16Kh12MVSFBR steel.