プラズマ溶射遮熱コーティングシステムの室温ならびに高温における機械的損傷挙動のその場観察

概要

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In situ observation of the mechanical failure behavior was conducted for different kinds of the plasma sprayed thermal barrier coating (TBC) systems by means of an optical microscopy under the static loadings at ambient and elevated temperatures; as the fundamental aspect, in order to clarify the thermo-mechanical failure mechanism in connection with various coating characteristics. Mechanical tensile or compressive loading was applied progressively to the TBC specimen by an axial loading manner. It was found that the failure behavior of TBC system depends strongly on the testing temperature under both the tensile and compressive loadings. Namely, at the elevated temperature which is higher than the ductile-brittle transition temperature (DBTT) of metallic CoNiCrA1Y bond-coat (BC), the ceramic yttria-stabilized zirconia (YSZ) topcoat (TC) spalling can be prevented effectively by virtue of the strain accommodation due to the extensive plastic flow in the BC layer. At the ambient temperature which is lower than the DBTT of BC, on the contrary, the TC spalling is more pronounced as a strain increases regardless of stress direction. Such an initiation site of TC spalling is closely related with the magnitude of local plastic deformation in the alloy substrate. Furthermore, the influence of coating microstructures on the crack initiation and propagation behavior was investigated in detail.
社団法人日本材料学会の論文
2006-12-15