Intermetallic Compounds for High-Temperature Structural Use UNIQUE IRIDIUM AND RUTHENIUM COMPOUNDS

Materials that are strong at progressively higher temperatures are sought for use in aircraft engines, in order that operating temperatures, and thereby efficiency and performance, can be increased. Intermetallic compounds with high melting temperatures have the promise of higher strength and elastic stiffness while hot, but in most cases they suffer from extreme brittleness at room temperature. An extensive experimental search of intermetallics has identified four binary compositions that are tough at ambient temperature; and, curiously, each compound has a platinum group metal as one of its components. They are AlRu, IrNb, RuSc, and RuTa. It is unlikely that the costs of these compounds will allow practical turbine blades to be made in the near future. Nevertheless, the existence of favourable properties is encouraging, in that, by further alloying of the base structures and compositions, one or more of them might be transmuted into commercial materials which would still depend on ruthenium or iridium for their good properties.