Effect of 730 °C Supercritical Fluid Exposure on the Fatigue Threshold of Ni-Based Superalloy Haynes 282

Driven by the need to reduce CO2 emissions from fossil power generation, new turbine working fluids are being investigated. One such fluid, supercritical carbon dioxide (sCO2), offers potential for improved energy conversion efficiency. In situ corrosion studies on precipitate-hardened nickel superalloys in sCO2 have shown potentially dangerous subsurface depletion of gamma prime phase. In the present work, the ex situ effect of supercritical fluid exposure on fatigue crack growth thresholds was measured for the Ni-based superalloy Haynes 282. After exposure of 500 h at 730 °C, there was a small measurable and repeatable reduction in fatigue thresholds at room temperature from 13 to 11 MPa√m after exposure. This reduction in fatigue crack growth threshold occurred irrespective of the exposure environment and was attributed to a decrease in roughness-induced crack closure.