The Effect of Environment and Material Chemistry on Single-Effects Creep Testing of Austenitic Stainless Steels

Injected vacancy, enhanced creep is hypothesized to reduce crack growth rates (CGRs) in deaerated pressurized water (DPW) in austenitic stainless steels with high sulfur levels. CGR reduction is hypothesized to occur by corrosion generated vacancy/dislocation interactions that promote dislocation climb and disrupt planar slip bands. Creep tests using tensile specimens of varying sulfur content were performed in air and DPW at 288 °C. Testing began with a hold at the flow stress, followed by fatigue cycles at room temperature (RT), then holds at flow stress and 105% flow stress. Primary creep was exhibited in the high sulfur material in DPW, after the RT fatigue cycles, and resulted in 0.19 mm of extension. Characterization revealed a corrosion product and a deformed microstructure with extensive planar slip bands in the specimen that crept. Corrosion-generated vacancies are unlikely to be the source of the primary creep. Potential mechanisms for the observed creep behavior will be discussed.