Effect of Grain Size on Low Cycle Fatigue Life in Compressor Disc Superalloy GH4169 at 600 °C

A microstructure‐based homogenization model for predicting the low‐cycle fatigue initiation life of GH4169 superalloy

“…5 Besides, microcracks tend to initiate from inclusions near or at the surface due to the stress concentration caused by the surface defects 8 and the volume expansion mismatches produced by the high temperature oxidation of inclusions. 8,9 The microstructurally small crack growth behavior is also affected by the microstructure. Obvious fluctuations of the small crack growth rates are found in the experiment observation due to the scatter of local microstructure.…”

“…Except for the influence of the relative sizes, microcracks under fatigue loading are often caused by the interfacial separation as the bonding effect between inclusions and the matrix is weak. 4,8 At high stress level (higher than the elastic limit), brittle inclusions are likely to break as they can't adapt to the deformation, which will incubate microcracks at inclusions. 5 Besides, microcracks tend to initiate from inclusions near or at the surface due to the stress concentration caused by the surface defects 8 and the volume expansion mismatches produced by the high temperature oxidation of inclusions.…”

“…4,8 At high stress level (higher than the elastic limit), brittle inclusions are likely to break as they can't adapt to the deformation, which will incubate microcracks at inclusions. 5 Besides, microcracks tend to initiate from inclusions near or at the surface due to the stress concentration caused by the surface defects 8 and the volume expansion mismatches produced by the high temperature oxidation of inclusions. 8,9 The microstructurally small crack growth behavior is also affected by the microstructure.…”

“…By distinguishing two incubation mechanisms of the microcracks, the scatter of the fatigue life can be reduced. 11 Microstructure influences on the LCF initiation life have been considered in previous works by introducing microstructure parameters as grain size 8,12 and inclusion size 13 into the equation coefficient of the phenomenological models. With experiment measured microstructure parameters and statistical approaches, phenomenological models have been used to model the effect of microstructure on the mean and worst-case fatigue life.…”

“…Both the two sites for fatigue cracks are found when the size of grains and inclusions is close. Except for the influence of the relative sizes, microcracks under fatigue loading are often caused by the interfacial separation as the bonding effect between inclusions and the matrix is weak 4,8 . At high stress level (higher than the elastic limit), brittle inclusions are likely to break as they can't adapt to the deformation, which will incubate microcracks at inclusions 5 .…”