Crack healing mechanisms in atmospheric plasma sprayed Yb-silicate coatings during post-process heat treatment. Issue 8 (July 2023)

• Record Type: Journal Article
• Authors: Bakan, Emine; Vaßen, Robert
• Is Part Of: Journal of the European Ceramic Society. Volume 43:Issue 8(2023)
• Page Start: 3684
• Page End: 3693
• Publication Date: 2023-07
• Subjects: Environmental barrier coating -- Atmospheric plasma spray -- Crystallization -- Crack healing -- Porosity; Ceramic materials -- Periodicals; Composite materials -- Periodicals; Matériaux céramiques -- Périodiques; Composites -- Périodiques; Ceramic materials; Composite materials; Periodicals; Electronic journals; 666.05
• DOI: 10.1016/j.jeurceramsoc.2023.02.005
• Languages: English
• ISSNs: 0955-2219

Abstract

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.