Creep Behavior of Ir-Nb and Ir-Zr Refractory Superalloys

Abstract

The microstructure stability and creep properties of Ir-base refractory superalloys (It-Nb and Ir-Zr) with an fcc and L1₂ two-phase structure were investigated. An orderly arrayed structure composed of cuboidal coherent L1₂ precipitates was observed in the Ir-Nb alloys. By a different heat treatment, a maze structure and a discontinuous coarsened lamellar structure were obtained in the Ir-Zr alloys. Creep behavior was investigated for samples with these three kinds of microstructure between 1500 and 1800°C. The creep behavior was explained according to microstructural changes before and after creep.