Transformation of Niobium Carbide in Heat-Resistant Alloys Based on Fe – 25Cr – 35Ni at 900°C and 1150°C

Cross sections prepared using a focused ion beam are used for a transmission electron microscopy study of the microstructure and elemental composition of the intermetallic phases formed after long-term holding a 900 and 1150°C at the boundaries of dispersed particles of niobium carbide in a heat-resistant alloy of type HP40NbTi. Formation of a well-known G-phase is detected at 900°C. When the temperature is raised to 1150°C, an fcc intermetallic phase with parameter a = 1.084 nm (space group Fd3m) is detected. The elemental composition of the high-temperature intermetallic compound and participation of atmospheric nitrogen in its formation are established.