Degradation of creep properties in single crystal superalloy IN792LC during long-term thermal exposure
The influence of long-term thermal exposure up to 3 000 h at 800℃on the microstructure evolution and creep behavior of the IN792 LC single crystal superalloy was investigated.The results reveal the uniform dispersion of the spheroidal growth of the γ'phase within the γ matrix after prolonged thermal exposure.The coarsening behavior of the γ'phase conforming to the Lifshitz-Slyozov-Wagner(LSW)model.The discontinuous carbides were precipitated around the eutectic after thermal exposure,but no topological close-packed(TCP)phase was generated.The creep tests were carried out at 760℃/662 MPa after long-term thermal exposure,the creep life of superalloy decreased due to the tissue degradation while the facture elongation increased as the thermal exposure time increased.Specifically,the creep fracture life dropped by 81.1%after 3 000h of thermal exposure.The reduction in creep life was mainly attributed to the coarsening of the γ'phase,degradation of the carbide,and increased creep porosity.Additionally,the decomposed MC carbide transformed into the M23 C6 carbide,which collapsed and gathered into micropores promote crack expansion.Furthermore,the dislocation network during creep was disrupted under thermal exposure and the dislocations cut through the γ'phase movement,which further reducing the creep fracture life.The results provide a reference for the service life prediction of IN792 LC single crystal superalloy at service temperature.
single crystal superalloythermal exposuremicrostructure degradationcreepcarbide
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