Thermodynamic modelling of the Cr–Nb–Si system

Abstract

Niobium silicide based refractory composite alloys have great potential for applications as the next generation turbine airfoil materials, owing to their significantly higher operating temperatures than advanced Ni-based superalloys. Thermodynamic description of the Cr–Nb–Si system is important for the development of niobium silicide based composite materials. In this work, a thermodynamic assessment of the Cr–Nb–Si system is carried out, using the CALPHAD method together with predictions based on Miedema's macroscopic-atomic model and ab initio density functional theory. Phase diagrams calculated using the current thermodynamic description are in good agreement with available experimental data. The modelling results also lead to suggestions of alloy compositions, which deserve further experimental investigation. The description of the current work is a step forward for a full thermodynamic description of Nb–Si–Cr–Ti–Hf–Al system, the basis for developing potential composite alloys based on niobium silicides.