Effect of Heat-to-Heat Variability on Long-Term Creep Rupture Lifetime Predictions of Single Step Aged Wrought Haynes 282 Alloy

Abstract

The impact of a weaker heat of the wrought form of Haynes 282 nickel superalloy on predicted 100,000 h creep rupture strength (CRS) and hence maximum allowable working stress (MAWS) was determined by correlating the creep rupture data of the two stronger heats of material that were used (along with the third weaker heat) to develop the ASME Code Case for this alloy. In comparison with the established MAWS values, estimated MAWS values were 3–7% higher in the temperature range of 700–800 °C and up to 30% higher above 800 °C when the weaker heat was removed from the data analysis. These results show the importance of minimizing heat to heat variability of properties that affect high temperature creep strength, including grain size, which can be affected by parameters that might not be included in the alloy specification. For nickel superalloys, such as Haynes 282, design optimization and manufacturing control of grain size, in addition to chemical composition and gamma prime content and size, can provide measurable improvements in MAWS values established by ASME in the time-dependent region, where these alloys are usually employed.