Identification of precipitate phases in a 11Cr ferritic/martensitic steel using electron micro-diffraction☆

Abstract The precipitate phases in a 11Cr ferritic/martensitic steel normalized at 1050 °C for 1 h followed by tempered at 750 °C for 2 h have been studied through electron micro-diffraction combined with EDX analysis. Two niobium-rich carbonitride phases, (Nb 0.75 V 0.15 Cr 0.1 )(C,N) and (Nb 0.5 V 0.4 Cr 0.1 )(C,N), with the same f.c.c. structure were identified. Three vanadium-rich carbonitride phases were identified to be (V 0.65 Nb 0.15 Cr 0.2 )(C,N), (V 0.45 Nb 0.45 Cr 0.1 )(C,N) and (V 0.55 Nb 0.25 Cr 0.2 )(C,N) with the same f.c.c. structure. Chromium-rich carbonitride M 2 (C,N) and chromium-rich carbide M 23 C 6 phases with a hexagonal and a f.c.c. crystal structure as well as a typical chemical formula of (Cr 0.8 V 0.2 ) 2 (C,N) and (Cr 0.7 Fe 0.25 W 0.05 ) 23 C 6 , respectively, were also identified in the steel sample. The size of each kind of precipitate phase was examined. The morphologies and precipitation sites along with the amount of observed precipitate phases were described and discussed.