Influence of a Thermal Barrier Coating on the High Temperature Low Cycle Fatigue of the Substrate

概要

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A thermal barrier coating (TBC) is employed in gas turbine hot parts. The TBC system is complicated materials system because it consists of a substrate, a blast layer, a bond-coat and a TBC top-coat. In order to understand the influence of the TBC top-coat on the high temperature low-cycle fatigue of the substrate, the fatigue tests at 405°C and 900°C were carried out on the four specimens, a bare substrate, a substrate with blasting, a specimen with blasting and bond-coating, and a TBC specimen with full process. It is understood from the test result that each three treatment decreases the life of the substrate and the life of the TBC specimen is the shortest. It was also confirmed that the coatings share the load for the substrate, which was positive factor for the substrate. However, under the low-cycle fatigue condition, the blasting decreases the life of a bare specimen because of roughness effect. The coatings also decrease the life of the substrate with blasting because of coating cracks. It was found that the coating damage was dominant for the life of the substrate under the low-cycle fatigue.