Effect of Alloying Additions on the Phase Equilibria and Oxidation in the Mo-Si-B System

摘要

The Mo-Si-B alloys containing the Mo metal phase in equilibrium with the Mo3Si and Mo5SiB2 intermetallic phases have potential as hot-section materials for jet engines. For high-pressure turbine blade application, the ternary Mo-Si-B compositions exhibit adequate oxidation resistance in the temperature range of 1000 to 1300 deg C, but below 1000 deg C, the oxidation resistance is not good. The present study was undertaken to explore the effect of a number of alloying additions to a ternary Mo-Si-B Base on improving the oxidation resistance. Microstructures and phase equilibria were determined at selected temperatures of quaternary and quinary alloys. The elements added were W, Nb, V, Cr, Re, Ge, Al, Hf and Ti + Cr. These alloys did not produce a better oxidation resistance-composition than the base ternary Mo-Si-B alloy.