Use of the Wilshire Equations to Correlate and Extrapolate Creep Data of HR6W and Sanicro 25.

Vito Cedro,Christian Garcia,Mark Render

doi:10.3390/ma11091585

Vito Cedro, Christian Garcia + Show 1 more

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https://doi.org/10.3390/ma11091585

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Abstract

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. Many methods have been proposed to extrapolate creep life, and one of recent significance is a set of equations known as the Wilshire equations. With this method, multiple approaches can be used to determine creep activation energy, increase the goodness of fit of 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 equation is used to extrapolate the creep life of HR6W and Sanicro 25, and different methods to determine creep activation energy, region splitting, the use of short-duration test data, and the omission of very-short-term data are investigated to determine their effect on correlation and calculations. It was found that using a known value of the activation energy of lattice self-diffusion, rather than calculating from each data set, is both the simplest and most viable method to determine . Region-splitting improved rupture time calculations for both alloys. Extrapolating creep life from short-term data for these alloys was found to be reasonable.

Highlights

Innovations in power generation require materials that are capable of withstanding high temperatures and stresses for at least 100,000 h of operation time
The high temperatures and pressures found in advanced power plants can induce creep failure in alloys
The Wilshire equation for times taken to rupture and the Larson-Miller parameter (LMP) equation are used to correlate and extrapolate the creep life of HR6W and Sanicro 25, which are recently commercialized, high-Cr, austenitic stainless-steel alloys

Summary

Introduction

Innovations in power generation require materials that are capable of withstanding high temperatures and stresses for at least 100,000 h of operation time. The high temperatures and pressures found in advanced power plants can induce creep failure in alloys. Creep data of new and advanced power plant alloys are often not available at the times relevant to the required design life. Various methods have been proposed to extrapolate creep life using data collected from short-duration tests. The Wilshire equations [1] are a recently-developed extrapolation method that have been used to predict long-term creep behavior of high-temperature, creep-resistant alloys [2]. Different approaches have been used to fit the Wilshire equation to creep rupture data. The Wilshire equation for times taken to rupture and the Larson-Miller parameter (LMP) equation are used to correlate and extrapolate the creep life of HR6W and Sanicro 25, which are recently commercialized, high-Cr, austenitic stainless-steel alloys. The Wilshire equation’s goodness of fit and the error of the calculated

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