A microstructural rafting state-based constitutive model for single crystal Ni-based superalloys at elevated temperature

Microstructure degradation and residual low cycle fatigue life of a serviced turbine blade

“…The widening γ channel decreases the Orowan stress and thus facilitates the dislocations movement in the γ channel. 7 Meanwhile, more dislocations uniformly distribute along the γ/γ 0 interface to generate the dislocation network, for which the dislocations are hindered in the γ channel by γ 0 precipitate. 44 Coarsened γ/γ 0 structure is likely to therefore exhibiting more homogeneous slip character with the form of dislocation loops by a combined glide-climb process.…”

“…4,5 However, the particle-strengthening effect is greatly influenced by the configuration of γ/γ 0 phases. 6,7 After servicing under severe environment, the microstructure of the blades undergoes significant degradation, 8,9 which consequently influences the hightemperature mechanical properties, particularly the LCF properties of the blades. [10][11][12][13] Previous studies [14][15][16] have summarized the typical microstructural degradations in turbine blades, which includes the coarsening and rafting of γ 0 precipitate, the decomposition of primary MC carbide, the evolution of grain boundary (GB) and GB precipitates as well as the evolution of topologically close-packed (TCP) phase.…”

“…Unlike other forms of local microstructural degradation, coarsening and rafting represent the overall degradation of the alloys. 7 The change of the configuration of γ/γ 0 phases directly weakens the particle-strengthening mechanism, which reduces the plastic deformation resistance. 4,17 This results in the reduction of yield strength and the accelerating accumulation of fatigue damage.…”

“…The γ′ precipitate plays a key role in conferring strength to the superalloy 4,5 . However, the particle‐strengthening effect is greatly influenced by the configuration of γ/γ′ phases 6,7 . After servicing under severe environment, the microstructure of the blades undergoes significant degradation, 8,9 which consequently influences the high‐temperature mechanical properties, particularly the LCF properties of the blades 10–13 …”

A thickness‐sensitive and orientation‐related creep lifetime prediction method of nickel‐based single crystal superalloy

“…There are obvious rafting behaviors during the creep process of nickel‐based single crystal superalloy, and local modifications of stress/strain fields around pores involve modifications of γ/γ’ microstructure (specifically the width of γ matrix channels) 22,23 . For deformation behavior prediction of nickel‐based single crystal superallys, the degradation of microstructure (such as rafting and coarsening) brings new challenges, and the microstructure‐sensitive constitutive models are proposed through introducing new internal variables about the evolutions of rafting and coarsening 24,25 . However, the existing prediction methods of creep lifetime and deformation behavior considering anisotropy mainly focus on the specimens with specific thickness, and few of these methods could reflect the thickness debit effect.…”