Use of the Wilshire equation to correlate and extrapolate creep rupture data of Incoloy 800 and 304H stainless steel

Advanced power plant alloys must endure high temperatures and pressures for durations at which creep data are often not available, necessitating the extrapolation of creep life. A recently developed creep life extrapolation method is the Wilshire equation, with which multiple approaches can be used to increase its goodness of fit to available experimental data and improve the confidence level of calculating long-term creep strength at times well beyond the available experimental data. In this article, the Wilshire and Larson-Miller parameter equations are used to extrapolate the creep life of Incoloy 800 and 304H stainless steel to 100,000 h. The use of (1) different methods to determine creep activation energy, (2) region splitting, and (3) short-duration test data to predict long-term failure were investigated to determine their effects on correlation and extrapolation using the Wilshire equation. The accuracy of the Wilshire and Larson-Miller parameter equations' calculated times to rupture are compared.