MICROSTRUCTURAL EVOLUTION AND RESIDUAL STRESSES OF AIR-PLASMA SPRAYED THERMAL BARRIER COATINGS UNDER THERMAL EXPOSURE

Jae-Young Kwon, Jae-Hyoun Kim, Sang-Yeop Lee, Yeon-Gil Jung (), Hyun Cho, Dong-Kee Yi and Ungyu Paik
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Jae-Young Kwon: School of Nano and Advanced Materials Engineering, Changwon National University, #9 Sarim-dong, Changwon, Kyungnam 641-773, Korea
Jae-Hyoun Kim: School of Nano and Advanced Materials Engineering, Changwon National University, #9 Sarim-dong, Changwon, Kyungnam 641-773, Korea
Sang-Yeop Lee: School of Nano and Advanced Materials Engineering, Changwon National University, #9 Sarim-dong, Changwon, Kyungnam 641-773, Korea
Yeon-Gil Jung: School of Nano and Advanced Materials Engineering, Changwon National University, #9 Sarim-dong, Changwon, Kyungnam 641-773, Korea
Hyun Cho: Department of Nanosystem and Nanoprocess Engineering, Pusan National University, Miryang, Kyungnam 627-706, Korea
Dong-Kee Yi: Division of Bionanotechnology, Kyungwon University, Bokjung-dong, Sungnam, Gyeonggi 461-701, Republic of Korea
Ungyu Paik: Department of Energy Engineering, Hanyang University, Haengdang-dong, Sungdon-gu, Seoul 133-791, Korea

Surface Review and Letters (SRL), 2010, vol. 17, issue 03, 337-343

Abstract: Microstructural evolution and fracture behavior of zirconia(ZrO2)-based thermal barrier coatings (TBCs) were investigated under thermal exposure. NewZrO2granule with 8 wt.% yttria (Y2O3) with a deformed hollow morphology was developed through a spray drying process and employed to prepare TBCs. The thermal exposure tests were conducted at 1210°C with a dwell time of 100 h till 800 h. The residual stress at the interface between top coat and thermally grown oxide (TGO) layer was measured using a nanoindentation technique before and after thermal exposure. Vertical cracks on the top coat were newly formed and interlamellar cracks at the interface were enhanced after the thermal exposure of 800 h. Especially, partial delamination was observed at the interface after the thermal exposure of 800 h in TBC samples tested. The microstructural evolution in the top coat could be defined through load–displacement curves, showing a higher load or a less displacement after the thermal exposure of 800 h. The stress state was strongly dependent on the TGO geometry, resulting in the compressive stresses at the "valleys" or the "troughs," and the tensile stresses at the "crests" or peak areas, in the ranges of -500 to -75 MPa and of +168 to + 24 MPa, respectively. These stress terms incorporated with resintering during thermal exposure affected the mechanical properties such as hardness and elastic modulus of the top coat.

Keywords: Thermal barrier coating (TBC); microstructure; interface; thermally grown oxide (TGO); residual stress (search for similar items in EconPapers)
Date: 2010
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DOI: 10.1142/S0218625X10013965

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