According to the service loads experienced by air cooled single crystal turbine blades

thermomechanical fatigue (TMF) experiments were designed and conducted on thin-walled tube specimens made of nickel based single crystal superalloy DD6. The results indicated that the deformation response of DD6 exhibited remarkable ratcheting effect

which was closely related to the phase angle and mechanical loading; and the lifetime of in phase (IP) TMF under all experiment conditions were shorter than that of out of phase (OP) TMF. Either introducing dwell time at peak temperature or increasing mechanical load led to more ratcheting strains and fewer failure cycles. Based on the metallographic examination on fracture surface and longitudinal section of specimens

the critical life-limiting factors under different load conditions were identified. Creepage and fatigue dominate in the competing damage mechanisms for IP TMF

while oxidation and fatigue dominate for OP TMF.