The role of coarsening on LCF behaviour using small coupons of a DS Ni-based superalloy

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

“…Some previous studies carried out by the authors show similar deformation features. 11,13 Besides, the severe deformation morphology of γ/γ 0 phases in the deformed zone reveals a significant reduced resistance to plastic deformation of the coarsening superalloy, which exacerbates the cyclic softening behavior of the 2.0 TBO blade shown in Figure 12.…”

“…Extensive investigations have demonstrated that the degradation of γ 0 precipitate, such as coarsening and rafting, reduces the mechanical properties of the Nibased superalloy. 11,32 The statistical feature data make it possible to establish reliable relationship between mechanical properties and the microstructure characteristics. Therefore, the quantitative characterization of coarsening is of significant benefit for assessing the residual service life, as well as for decommissioning decisions of the turbine blades.…”

“…A similar relationship is also established in a DS Ni-based superalloy that underwent rafting process 13 and coarsening process. 11 This indicates that it is appropriate to employ the logarithmic form life model to describe the LCF life consumption resulting from microstructure degradation of γ/γ 0 phases under real service conditions of the blade.…”

“…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.…”

“…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 …”