Creep behaviors of an Ir-23Nb alloy at ultra-high temperatures

The ultra-high-temperature creep behaviors of an Ir-base, Ir-23Nb (in at. pct), two-phase refractory superalloy have been investigated. The compression creep experiments were performed at temperatures from 1650 °C to 1800 °C at initial applied stresses from 49 to 200 MPa. The results show that Ir-23Nb alloy has higher creep resistance and longer creep life in comparison to Ir-17Nb alloy under the same experimental conditions. The steady-state creep behavior can be described in terms of power-law creep with the apparent stress exponent of 4.5 and apparent activation energy of 653 kJ/mol. Basing on the investigation, the possible reasons for the great improvement on the creep resistance and creep life in Ir-23Nb alloy are discussed. This article is based on a presentation made in the symposium entitled “Fundamentals of Structural Intermetallics,” presented at the 2002 TMS Annual Meeting, February 21–27, 2002, in Seattle, Washington, under the auspices of the ASM and TMS Joint Committee on Mechanical Behavior of Materials.