Creep rupture properties of a nickel-base heat-resistant alloy Hastelloy XR under varying temperature/stress condition

A series of constant temperature and load creep rupture tests and varying temperature and/or load creep rupture tests was carried out on a nickel-base heat-resistant alloy Hastelloy XR, which was developed for applications in the High-Temperature Engineering Test Reactor, at 850 to 1000degC in the simulated HTGR helium gas. This report describes the applicability of the conventional creep damage rules, i.e., the life fraction, the strain fraction and their mixed rules, to the alloy. The applicability was examined using the data under varying both temperature and load conditions as well as those, which were obtained in the previous work, under constant temperature and varying load conditions. The life fraction rule showed the best applicability of these three criteria. The good applicability of the rule was considered to show that the change of the chemical composition and/or the microstructure during exposure to the high-temperature simulated HTGR helium environment was not appreciable to affect the creep strength of Hastelloy XR. Though the life fraction rule under varying both temperature and load conditions is slightly less applicable than that under constant temperature and varying load conditions, it has been concluded that the rule is applicable in engineering design of high-temperature components made of Hastelloy XR. (author)