A Local Approach to Creep-Fatigue -Oxidation Interactions in Inco 718 Alloy

摘要: Understanding and modeling hold time effects on fatigue crack growth rate (FCGR) above 500 °C in Inco 718DA is a great challenge. Fatigue tests with trapezoidal wave shape signal including times from 90 s to 3600 were carried out small grain size (5-15 μm) over wide range of temperatures (500 °C-650 °C). FCGRs measured using potential drop technique. SEM observations correlate the trans- or inter-granular aspect fracture surfaces. Two regimes must be distinguished. The first regime associated relatively short can represented by power law, where da/dN proportional tα, α ~ 0.25. This corresponds situation does not propagate during but its propagation takes place cyclic part loading damaged zone ahead tip. second longer case (creep growth) predominant. purely dependent. Simple models are introduced describe both regimes.