Precipitate phases in normalized and tempered ferritic/martensitic steel P92

Abstract Ferritic/martensitic steel P92 is a promising candidate for cladding and duct applications in Sodium-Cooled Fast Reactor. The precipitate phases of the P92 steel normalized at 1323 K (1050 °C) for 30 min and tempered at 1038 K (765 °C) for 1 h have been investigated using transmission electron microscopes. Four types of phases consisting of M 23 C 6 , MX, M 2 X and sigma-FeCr were identified in the steel. MX phases consist of Nb-rich M(C,N) carbonitride, Nb-rich MC carbide, V-rich M(C,N) carbonitride, V-rich MC carbide, V-rich MN nitride, and complex MC carbides with Nb-rich MC core and V-rich MC wings. M 2 X phases consist of Cr-rich M 2 (C,N) carbonitride, Cr-rich M 2 C carbide and M 2 N nitride. Sigma-FeCr has a simple tetragonal lattice and a typical chemical formula of Fe 0.45 Cr 0.45 W 0.1 . M 23 C 6 and MX are the dominant phases, while the sigma-FeCr has the lowest content. The formation of sigma-FeCr and M 2 X phases in the steel is also discussed.