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A typical TBC system consists of a ceramic top coat material, such as 7–8% yttria stabilized zirconia, applied over a metallic bond coat material, such as diffusion aluminide or MCrAIY. The bond coat serves as an oxidation protection layer for the substrate, as well as providing an adherent surface for the ceramic top coat layer. Estimation of coating durability is critical for design of highly reliable TBC coated parts. Laboratory testing and historical engine experience have revealed that TBC can degrade by various mechanisms; such as fatigue, oxidation, erosion, and impact. Mechanism-based life prediction techniques are needed to assess the durability of TBC in a simulated gas turbine service cycle consisting of: start-up to full speed, steady state operation at full load, and shut-down to zero speed. New testing protocols have been developed in order to simulate the TBC loading under these conditions. The lifing methodology has been calibrated using GE Power Systems gas turbine experience. A nondestructive technique was also used for evaluation of pre- and post-tested TBC specimens.

In this article, the quasi-static and cyclic fatigue fracture behavior of aluminum alloy 2014 discontinuously reinforced with fine particulates of aluminum oxide are presented and discussed. The discontinuous particulate-reinforced 2014 aluminum alloy was cyclically deformed under fully reversed, tensioncompression loading over a range of strain amplitudes, well within the plastic domain of the engineering stress-strain curve, resulting in cyclic fatigue lives of less than 10 4 cycles. The influence of both ambient and elevated temperatures on cyclic stress and cyclic stress-strain response is highlighted. The underlying mechanisms governing the fracture mode during quasi-static and cyclic fatigue are discussed and rationalized in light of the concurrent and mutually interactive influences of intrinsic composite microstructural features, deformation characteristics of the metal matrix and reinforcement particulate, cyclic strain amplitude and resultant fatigue life, and test temperature.

In this article, the quasi-static and cyclic fatigue fracture behavior of aluminum alloy 2014 discontinuously reinforced with fine particulates of aluminum oxide are presented and discussed. The discontinuous particulate-reinforced 2014 aluminum alloy was cyclically deformed under fully reversed, tensioncompression loading over a range of strain amplitudes, well within the plastic domain of the engineering stress-strain curve, resulting in cyclic fatigue lives of less than 10 4 cycles. The influence of both ambient and elevated temperatures on cyclic stress and cyclic stress-strain response is highlighted. The underlying mechanisms governing the fracture mode during quasi-static and cyclic fatigue are discussed and rationalized in light of the concurrent and mutually interactive influences of intrinsic composite microstructural features, deformation characteristics of the metal matrix and reinforcement particulate, cyclic strain amplitude and resultant fatigue life, and test temperature.

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