13th International Conference on Fracture June 16–21, 2013, Beijing, China -5- (a) da/dN versus f (b) da/dN versus ΔK Figure 2. Comparisons between the fitted and experimental da/dN of FGH97 at 750 °C 4. Applicability on Alloy 718 and Hastelloy® X In order to verify the applicability of the model on other materials, two additional nickel-based superalloys from the references, namely Alloy 718 and Hastelloy® X, were analysed. Alloy 718 is a wrought polycrystalline nickel based superalloy with a large amount of Fe and Cr. The crack growth experiments [8] were conducted on Kb-type specimens with rectangular cross sections of 4.3×10.2 mm. Hastelloy® X alloy is a solid-solution strengthened nickel-based superalloy that combines exceptional oxidation resistance, good fabricability, and excellent high-temperature strength. And the experiments [9] were conducted on CT specimen with thickness of 3.2 mm, height of 61.0 mm and width of 63.5 mm. Here, two temperatures with three or four dwell times were involved for each material. Details of the experiments can be found in references [8] and [9], respectively. Figure 3 and Figure 4 present the comparisons between the fitted and experimental da/dN of Alloy 718 and Hastelloy® X, respectively. Where, the solid lines in the figures were fitted by Eq. (4). Encouragingly, the results show excellent correspondences for these two alloys.
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