CREEP RUPTURE PROPERTIES OF A NI-CR-W SUPERALLOY IN AIR ENVIRONMENT

摘要

The creep rupture properties in air environment were studied at 900, 1000 and 1050 degrees C for bar, plate and seamless tube materials of a Ni-Cr-W superalloy developed for use at service temperatures around 1000 degrees C. The long-term creep rupture strength is estimated by applying the time-temperature parameter method to the creep rupture data. Data of anomalous behaviour due to oxidation strengthening, which is observed in creep curves with rupture times above similar to 10000 h at 1000 degrees C, are corrected for the application of the time-temperature parameter method. The Larson-Miller parameter method is better than the Orr-Sherby-Dorn parameter method in respect of curve fitting to the present creep rupture data. The creep rupture strength of the bar material with grain sizes above ASTM No. 2 and of the plate material is above 9.8 MPa for a 1 x 10(5) h life at 1000 degrees C, which is the final target of this program. The creep rupture strength increases with increasing grain size and heat treatment temperature. (C) 1997 Elsevier Science B.V. [References: 19]