CREEP-PROPERTIES UNDER VARYING STRESS TEMPERATURE CONDITIONS ON NICKEL-BASE HEAT-RESISTANT ALLOY HASTELLOY XR

A series of constant load & temperature creep tests and varying load and/or temperature creep 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 temperatures ranging from 850 to 1,000-degrees-C in order to examine the creep behaviors of the alloy under varying load and/or temperature conditions. The minimum creep rate was not affected by the prior exposure to the load and temperature environment. The life fraction rule showed a good applicability among various prediction rules. Above-mentioned two items, i.e. no change of the minimum creep rate and the good applicability of the life fraction rule were considered to show that the change of the chemical composition and/or the microstructure during exposure to the high-temperature simulated HTGR helium gas environment was not appreciable to affect the creep strength of Hastelloy XR.