Mechanisms of damage and fracture in high-temperature, low-cycle fatigue of a cast nickel-based superalloy
In cast Udimet 500 subjected to high-temperature, low-cycle fatigue, localized oxidation at grain boundaries plays an important role in crack nucleation and propagation. Evidence is presented of a surface ridging and pronounced grain boundary penetration due to oxidation, a denudedγ′ zone adjacent to the oxide, and cracking of the oxide. The ridging is selective, and is presumed to occur on those boundaries where high stress exists. The phenomenon is viewed as analogous to stress-corrosion cracking.
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