High Temperature Oxidation in Multicomponent Nb Alloys
Niobium-Silicon alloys offer potential as a new generation of refractory material system that could meet the high-temperature capability envisaged to exceed the application temperatures of Ni base superalloys. A serious concern in the application of Nb based alloys is their poor oxidation resistance at elevated temperatures. The ternary diagram Nb-Ti-Si system exhibits eutectic groves nearly parallel to the Nb-Ti binary and terminate in a Class II invariant reaction, L+(Nb,Ti)3Si → β+ (Ti,Nb)5Si3. A peretectic ridge from the reaction, L+(Nb,Ti)5Si3 →(Nb,Ti)3Si also exists and these reactions control the microstructures resulting from solidification of these Nb alloys. The microstructures associated with these alloys comprise a distribution of Nb5Si3 in β matrix. The effect of various alloying elements on the resulting microstructures are illustrated The effect of microstructural distribution on oxidation resistance of multiphase alloys are also discussed.
Z.Y. Zhong, H. Saka, T.H. Kim, E.A. Holm, Y.F. Han and X.S. Xie
E. S. K. Menon and M. G. Mendiratta, "High Temperature Oxidation in Multicomponent Nb Alloys", Materials Science Forum, Vols. 475-479, pp. 717-720, 2005