On the Mechanical Response in a Thermal Barrier System Due to Martensitic Phase Transformation in the Bond Coat

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Recent studies have shown that Pt-aluminide—a common bond coat material in thermal barrier coatings—undergoes martensitic transformations during thermal cycling. The transformations are associated with both large transformation strain and a strain hysteresis, leading to accumulation of a mismatch strain. Thermal barrier systems based on Pt-aluminide bond coats are susceptible to interfacial morphological instabilities. In this study, we investigate how the cyclic martensitic transformation influences the morphology. Two key results are: (i) the morphological instabilities are highly sensitive to the thermo-mechanical properties of the substrate due to the martensitic transformation; (ii) the hysteresis associated with cyclic martensitic transformation cannot drive the morphological instabilities; the strains associated with the formation of the thermally grown oxide do.

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