THE INFLUENCE OF OXIDATION ON THE LIFE TIME OF THERMAL BARRIER COATINGS

摘要

Bond coat oxidation as well as bond coat depletion of Al are still believed to be major degradation mechanisms with respect to the life time of thermal barrier coating systems for both aero engines and land based gas turbines. However, the most recently proposed life time prediction models are starting to incorporate measurement data that provides semi-detailed information about the top coat and the thermally grown oxide degradation process. Three approaches currently under development have provided some interesting results with regards to the thermal barrier coating system degradation, namely interfacial adhesion (in the form of critical strain), thermally grown oxide damage accumulation (in the form of the physical defect kinetics), and thermally grown oxide mixed with top coat damage accumulation (in the form of acoustic emission analysis) at various stages of the life time of both atmospheric plasma sprayed and electron beam physical vapor deposited thermal barrier coating systems. It is expected that life time prediction models that utilize ex-situ and in-situ data that is sensitive to the thermal barrier coating system degradation would produce a more accurate prediction as well as provide insight into which high temperature phenomenon is dominating life time, such as, top coat sintering, bond coat oxidation, bond coat depletion of Al, thermal fatigue or mechanical fatigue.