Creep–Environment Interactions in Dwell-Fatigue Crack Growth of Nickel Based Superalloys

Critical Assessment 21: Oxygen-assisted fatigue crack propagation in turbine disc superalloys

“…Increases in the turbine entry temperature are needed to improve engine efficiency and reduce greenhouse gas emissions, so turbine disc alloys are increasingly being pushed to work at higher temperatures. 1 This temperature increase usually causes greater susceptibility to accelerated, environmentally related cracking, [17][18][19][20][21][22] especially during the take-off and landing stages of a duty cycle in an aeroengine. Thus, fatigue failure processes with environmental attack, particularly in oxygen-containing environments, should be evaluated thoroughly.…”

Fatigue crack growth mechanisms in powder metallurgy Ni-based superalloys—A review

“…In the dwell FCG tests conducted on PM superalloys, the enhanced FCG behaviour associated with the prolonged dwell time at the peak load can be ascribed to the creep and environmental damage during the dwell period [11,12,20,85,88,89,[104][105][106][107]. Similar to the stress relaxation processes at the crack tip, the creep processes at the crack tip are also closely related to the tertiary γ′ coarsening.…”

“…15. Although creep damage is claimed to be partially responsible for these accelerated FCG processes and creep damage may also result in intergranular fracture [20,21,106], the creep effect can be distinguished from the environmental damage effect by conducting fatigue tests in vacuum or low oxygen partial pressure conditions under different loading waveforms and frequencies [10,11]. As shown in Fig.…”

“…As damage tolerance design prevails in these more advanced aeroengines, the FCG behaviours and the associated mechanisms of PM Ni-based superalloys have received more and more attention. Moreover, FCG behaviours under dwell fatigue conditions in aggressive environments have become of increasing concern due to the increased turbine inlet temperatures which will cause more significant creep and environmental damage superimposed onto the fatigue damage processes and can accelerate the crack growth by one or two orders of magnitude [11,12,17,19,20]. Understanding the FCG behaviours and mechanisms operational in these service regimes for the new PM alloys is crucial for the development of more advanced disc alloys and their continued application in turbine discs.…”

A physics-based model for evaluating hot compressive dwell effects on fatigue crack growth in 319 cast aluminum alloys

“…A smaller body of work addressing subsequent crack growth, largely focuses on crack tip creep and environmental effects associated with hot tensile dwell or in-phase TMF, where the crack is open during the elevated temperature portion of the cycle for a substantial period of time. This type of crack growth is often characterized by highly localized creep [2,3] and/or environmentally-assisted fatigue crack growth phenomena [4,5] at the crack tip. A common approach is to represent the total crack growth rate, da/dN tot as the sum of timeindependent and time-dependent crack growth rates [6].…”