MoSi₂-Based Composite Materials for Aircraft Engines

MoSi2-based composite materials are among the advanced materials undergoing development as potential strong, stiff, lightweight replacements for the nickel-based superalloys now used in aircraft engines. Of the MoSi2-based composites, the most promising ones include SiC-based fibers within matrices that are, themselves, composites of MoSi2 containing 30 to 50 volume percent of Si3N4 particles. MoSi2 exhibits suitable high-temperature oxidation behavior, along with lower density and higher melting temperature relative to superalloys. However, the use of MoSi2 has been hindered by brittleness at low temperatures, inadequate resistance to creep at high temperatures, a coefficient of thermal expansion (CTE) much greater than that of SiC and other candidate fiber reinforcement materials, and a phenomenon called "pesting" (described in the next paragraph) at temperatures in the approximate range of 400 to 500 °C.