Superior thermo-mechanical fatigue property of a superalloy due to its heterogeneous microstructure

Thermo-mechanical fatigue of the [0 0 1]-oriented single crystal nickel base superalloy PWA-1480 was microstructurally investigated. Its superior fatigue property was evaluated in comparison with a single crystal nickel-base TMS-82 superalloy. During fatigue testing, a rafted γ/γ′ structure formed parallel to the [0 0 1] stress axis in PWA-1480. The deposited dislocations in the γ/γ′ interfaces lead to the appearance of misorientation (2-3°) locally between the γ and γ′ phases, resulting in a higher resistance for dislocation slip in the alloy. The rafted γ/γ′ structure can also effectively obstruct the propagation of a crack.