Various manners of degradation behavior for different kinds of heat-resistant coating systems were demonstrated on the basis of failure analysis for specimen subjected to the corrosive damage both through a practical service as gas turbine hot section component and in a laboratory experimental. Coating systems include Al diffusion coating, plasma spraying mainly for the thermal barrier coating (TBC). Main causes to enhance the coating failure can be classified into four types in relation with the thermal-mechanical-chemical aspects of coating properties. In particular, an importance of considering the simultaneous effect both of thermomechanical loading such as creep or fatigue, and of thermochemical loading such as hot corrosion was emphasized mainly for TBC degradation. Technical subjects for developing more advanced coating system also were briefly pointed out.
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