Specific Failures of Superalloys with Thermal Barrier Coatings Subjected to Thermo-Mechanical Fatigue Loadings with A Thermal Gradient in A Simulated Combustion Environment

摘要

A new test system has been developed which enables us to apply complicated thermo-mechanical fatigue (TMF) loadings to superalloy specimens in order to simulate the conditions and significant temperature gradients that are experienced in components that operate in a combustion gas flow environment. Employing this system, some TMF tests were carried out for superalloy specimens with thermal barrier coatings (TBCs) under a combined condition in which the external load was superimposed on the thermal cycles. Here, special attention was paid to the specific damage morphologies and the deformation under this kind of complicated TMF loadings. Based on the experimental results, a new mechanistic model was proposed for the specific failure modes, especially for a creep-induced ratcheting phenomenon as well as for failures of ceramic top coat. Finally, this understanding is summarized in a damage map, which is defined in terms of some mechanical criteria.