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Microstructural Evaluation of Laser Re-melted Columnar Thermal Barrier Coatings Produced by Suspension Plasma Spray
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DOI：10.1007/s11666-026-02308-0.png)
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Abstract
En 中文
Thermal barrier coatings (TBCs) protect turbine engine components allowing them to operate at high temperatures, significantly improving turbine power and fuel efficiency. Suspension plasma spraying (SPS), allows the creation of columnar microstructures with controlled porosity, thermal stresses, and lower thermal conductivity. However, the major challenge for the columnar structure is that it facilitates the penetration of calcium–magnesium–alumino-silicates (CMAS), which leads to TBC deterioration. To mitigate this, a laser post-treatment process has been proposed to re-melt the top layer of TBCs. In this study, columnar yttria-stabilized zirconia (8YSZ) topcoats were deposited by axial SPS. A CO2 laser treatment was used to create a re-melted layer at the surface of the SPS coatings. The influence of key laser parameters, such as scanning speed and laser power, on the microstructure of the re-melted top layer of the columns in the SPS coatings was investigated. Also, the micro-hardness, crack network and phase analysis of the laser re-melted layer were studied. The study showed that increasing the scanning speed increased the width of cracks of re-melted zone of TBC. Additionally, the laser glazing decreased surface roughness, sealed open porosity, produced a dense microstructure, and increased micro-hardness. The phase composition remained stable (metastable tetragonal (t′) phase) for both as-sprayed and laser-glazed samples. The primary objective of this study is to investigate the refinement of suspension plasma-sprayed (SPS) 8YSZ coatings through COâ‚‚ laser surface re-melting. Unlike traditional studies focused on sealing lamellar APS coatings, this work specifically targets the unique columnar microstructure inherent to SPS. The effects of laser power and scanning speed were optimized in relation to the re-melted layer thickness, crack width, and crack length. Furthermore, phase composition and microhardness analyses were conducted to evaluate the influence of laser glazing on the as-sprayed 8YSZ coatings.
Keywords:
columnar YSZ coating
laser treatment
suspension plasma spraying (SPS)
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