Fatigue & Fracture of Engineering Materials & Structures · 1979 · 87 citations · 8 references
Natural SciencesMaterials EngineeringMaterials ScienceMechanical Behavior Of MaterialsMetallurgyStructural MaterialsCreep BehaviorCreep DeformationFatigueFracture MechanicsHigh-temperature MaterialsNickel-based SuperalloysCrack GrowthCrack Growth KineticsCrack Growth RateFatigue Crack GrowthFatigue-creep InteractionGrain BoundariesHigh-temperature FatigueOxygen Diffusion
Abstract— This work was conducted to study the significant increases in fatigue crack growth rates at low frequencies commonly observed at high temperature. Creep tests and fatigue tests at 0·01, 0·1 and 1·0 Hz were conducted at 650°C in air and in helium on samples of INCONEL alloy 718 in two different heat treatments. Creep crack growth rates were 50–100 times greater in air than in helium. Fatigue tests in helium showed little sensitivity to frequency, but tests in air showed considerable increases in crack growth rates at lower frequencies. The results indicate the air environment played a predominant role in both the creep and the fatigue tests. Oxygen diffusion into grain boundaries appeared responsible for the accelerated crack growth in air. An overaging heat treatment reduced the crack growth rates.
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Creep crack growth in alloy 718
K. Sadananda, P. Shahinian · Metallurgical Transactions A · 1977 · 121 citations