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Vol.35, No.11, 1540 ~ 1547, 1997

Title

Microstructure and Mechanical Properties of Functionally Graded NiCrAlY / ZrO2 Thermal Barrier Coating Layers Fabricated by Plasma Spraying Technique

박차환 , 박익민 , 조경목 , 정명규 Cha Hwan Park , Ik Min Park , Kyung Mox Cho , Myung Gyue Jung

Abstract

Functionally graded thermal barrier coating(TBC) consisting of NiCrAlY and 8wt% Y₂O₃,-ZrO₂(YSZ) was produced on a Co-base superalloy (HAYNESS 188) substrate using the Ar shielded air plasma spraying method. Functional grading was obtained by the stepwise change of metal/ceramic composition. 1, 2 and 4 layers with different compsotional combinations were inserted between metal and ceramic layers. Microstructure of the functionally graded thermal barrier coating was examined to check proper grading of metal/ceramic compositions and features of defects. No particular defect which may affect the properties of TBS significantly was found at interface and through thickness of the graded layers even though some unavoidable oxides and pores were observed. Microstructural observation revealed successfully fabrication of functionally graded TBC by plasma spraying technique. A dhesion strength of TBC with 4 layers was measured with the highest value. In other words, the strength incerased with more smooth change of metal/ceramic composition within TBC. It assures the evidence that functional grading tend; to improve the strength removing the sharp interface and relieving the internal stress level due to the thermal mismach between metal and cermic.

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