Research progress on ultra-high-temperature Nb-silicide-based alloys

With higher melting points, relatively lower densities and good processability, Nb-Si based alloys show great promise for application as the next generation turbine airfoil materials with the operating temperature of 1 200-1 400 ℃. This paper introduces main research achievements of Beihang University in the field of ultra-high-temperature Nb-Si based alloys, mainly including alloying design, processing technologies (arc melting, induction melting, directional solidification, powder metallurgy), thermal protection coating material design and preparation technology and so on. Vacuum induction melting and precision molding with Y₂O₃ crucible are developed and used for successful preparation of simulated turbine blade. The liquid metal cooling directional solidification with Al₂O₃/Y₂O₃, Y₂O₃/Y₂O₃ crucible/mould is developed, with which the microstructures of directionally solidified Nb-Si based alloy are optimized to attain the balance of strength and toughness. Thermal protection coating material design and preparation technology are studied and great progress in high temperature oxidation resistance of alloy substrate and coating are attained.