Crack growth mechanisms at elevated temperature have been examined in a new nickel-based superalloy. Scanning electron microscopy has been used to identify the fracture modes in specimens tested under triangular, fast-slow, slow-fast, dwell and sustained loading conditions at 650 and 725 degrees C. A model has been developed considering a predominant oxidation-driven crack growth mechanism, as revealed from the SEM analysis. An oxidation sensitive time has been adopted to characterise the rate-dependent crack growth, together with an Arrehenius relationship to take account of the influence of temperature. The model predictions have been compared with the experimental results. (C) 2005 Springer Science + Business Media, Inc.