Thermal-mechanical fatigue behaviour and life prediction of oxide dispersion strengthened nickel-based superalloy PM1000

Many studies of thermal-mechanical fatigue behaviour address steels, nickel-base superalloys or fiber-reinforced titanium alloys, but only rough data are available for powder metallurgical high-temperature materials. In this study, the cyclic deformation and lifetime behaviour of the powder metallurgical nickel-base superalloy PM1000 were investigated under thermal-mechanical fatigue conditions. Thermal-mechanical fatigue tests were performed in the temperature range of 450-850 degrees C. The phase angle between the mechanical strain and the thermal cycle (-135 degrees) is closely related to the appropriate operating conditions in aero-engines. Thermal-mechanical fatigue results were compared with isothermal fatigue results reported in the literature for test temperatures of 850 and 1000 degrees C. Results revealed that isothermal fatigue exhibited a longer lifetime than thermal-mechanical fatigue at corresponding mechanical strain amplitude. in thermal-mechanical fatigue loading, cracks tended to initiate intergranularly and propagate transgranularly. Life prediction models were developed and compared to evaluate the possibility of predicting both thermal-mechanical fatigue and isothermal fatigue lifetimes. (C) 2008 Elsevier Inc. All rights reserved.