Crack healing mechanisms in atmospheric plasma sprayed Yb-silicate coatings during post-process heat treatment |
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| Affiliation: | 1. Department of Mechanical Engineering, Henan University of Engineering, Zhengzhou 451191, China;2. Department of Environmental and Biological Engineering, Henan University of Engineering, Zhengzhou 451191, China;3. Department of Civil Engineering, Henan University of Engineering, Zhengzhou 451191, China;1. Inner Mongolia Key Laboratory of Thin Film and Coatings, School of Materials Science and Engineering, Inner Mongolia University of Technology, Hohhot 010051, China;2. School of Chemical Engineering, Inner Mongolia University of Technology, Hohhot, China;1. Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research IEK-1, 52425, Jülich, Germany;2. University of Augsburg, Institute of Materials Resource Management, 86159, Augsburg, Germany |
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| Abstract: | The microstructural evolution of partially amorphous, atmospheric plasma-sprayed Yb-silicate coatings was investigated after heat treatment (HT, 1300 °C). Open porosity as well as crack area and widths in the coatings were characterized. A correlation was found between the increasing amorphous content of the as-sprayed coatings and the reduction in crack area due to crack healing after HT. Characterization results also suggested larger crack widths in the coatings after HT. The first crack-healing mechanism proposed was the capillarity-driven viscous flow of the amorphous phase in the coatings. It was experimentally shown that viscous flow-driven crack spheroidization (crack width enlargement), and crack healing started in the coatings at 1050 °C. Secondly, metastable to stable phase transformation (> 1100 °C) induced expansion in the constrained coatings was discussed as a crack healing mechanism. Finally, a two-step heat treatment was designed to prevent crack width enlargement during HT resulting in reduced porosity. |
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| Keywords: | Environmental barrier coating Atmospheric plasma spray Crystallization Crack healing Porosity |
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