In this paper fatigue and fracture of the Al-Al2O3-CrC, coatings have been investigated by in situ experiments performed in a scanning electron microscope. More importantly, micromechanical models using arrays of internal or surface cracks have been developed. The models provide mechanics of deformation and failure for the coating. The models also reveal the role of overloading in crack arrest, which may well be exploited in the safe design of toughened ceramics against fatigue. Initial overloads prior to cyclic loading are found to reduce significantly the crack driving force in post-overload fatigue crack growth. It expected that pre-service overloading has a great potential for improving the fatigue properties of composite coatings based on oxide ceramics and chrome carbide.

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