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The thermal-mechanical fatigue (TMF) behavior of cast K417 nickel-based superalloy was investigated under in-phase (IP) and out-of-phase (OP) loading in the temperature range from 400 to 850degreesC. The results revealed that the tendency to cyclic hardening Under thermal-mechanical and isothermal fatigue was higher than that Under static tensile testing at 850degreesC. Isothermal fatigue (IF) was observed to cause higher cyclic flow stress than TMF. At a corresponding strain amplitude, the thermal-mechanical fatigue life was lower than that of isothermal fatigue, and the TMF life of out-of-phase cycling was higher than that of in-phase cycling Scanning electron microscopic observations of fracture surfaces and longitudinal sections revealed intergranular-fatigue under in-phase TMF which led to the decrease in fatigue life. (C) 2002 Elsevier Science Ltd. All rights reserved.