Prediction of the phase composition of the refractory 45Cr26Ni33Si2Nb2 alloy in the process of stabilization

This paper is devoted to material aging in the operational temperature range of pyrolysis equipment. The EBSD analysis of the alloy phase composition after isothermal aging or stress-rupture tests at 800–1100°C for 1000–5000 h shows that the role of niobium and the two stable forms of its existence, namely, the G-phase Nb6Ni16Si7at a temperature below 900°C and carbide NbC above 1000°C, is crucial in the process of stabilization (thermodynamic equilibrium approach). The approximate dependences of the saturation concentration of carbon and the current concentration of carbides are in satisfactory agreement with numerical modeling and, at the same time, reveal the effect of temperature and doping either in a direct way (through the equilibrium constant, the specified concentrations of carbon, chromium, niobium) or via the activity coefficients of elements and their components. © 2014, Pleiades Publishing, Ltd.