| DING Qiheng,HU Lina,LEI Haijun,ZHANG Wenchao,HUANG Yankai.Surface Texture Design of 8YSZ Thermal Barrier Coating and Its Thermal Shock Resistance[J],53(15):224-233 |
| Surface Texture Design of 8YSZ Thermal Barrier Coating and Its Thermal Shock Resistance |
| Received:September 05, 2023 Revised:December 15, 2023 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2024.15.021 |
| KeyWord:thermal barrier coating surface texture thermal shock microstructure failure mechanism thermal shock resistance |
| Author | Institution |
| DING Qiheng |
School of Electrical Engineering, Xinjiang University, Urumqi , China |
| HU Lina |
School of Electrical Engineering, Xinjiang University, Urumqi , China |
| LEI Haijun |
Xinjiang Production and Construction Corps Development and Reform Commission, Urumqi , China |
| ZHANG Wenchao |
School of Electrical Engineering, Xinjiang University, Urumqi , China |
| HUANG Yankai |
State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, Wuhan , China |
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| Abstract: |
| Thermal barrier coatings (TBCs) provide thermal protection for high-temperature components in aero-engines and steam turbines. But thermal barrier coatings are prone to failure when exposed to cyclic thermal shock loads. To meet the increasing demand for device performance, optimizing surface texture has emerged as a promising strategy to extend the lifetime of TBCs. In this investigation, four surface textures (convex sine, concave semicircle, concave cosine, concave trapezoid) were processed on the substrate surface of nickel-based superalloys, and 8YSZ ceramic coating samples with equal thickness were prepared by atmospheric plasma spraying for the subsequent cyclic thermal shock test. A range of analytical techniques, including field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and energy disperse spectroscopy (EDS), were employed in this paper to scrutinize microstructural evolution, fracture morphologies, residual stress distribution during thermal shock as well as the elemental composition distribution related to the diffusion of oxygen and corrosive medium. Combined with the energy release rate criterion, the influence of the morphology of different surface textures on the failure mechanism was revealed. The findings highlighted the critical role of surface texture in enhancing the performance of TBCs. TBC samples without these textures exhibited lower interfacial toughness in tests, making them susceptible to cracks and voids at the boundaries and within the coating itself. This higher propensity to failure provided avenues for oxygen and corrosive permeation, ultimately leading to catastrophic fracture during water quenching. Furthermore, the study showed that convex textures, characterized by pronounced stress concentrations at their vertices, exhibited significantly elevated energy release rates. Consequently, this structure exhibited debonding failure after only 18 water quenching cycles. In stark contrast, the concave trapezoidal texture exhibited superior interfacial toughness, minimal internal residual stress, and an impressive average thermal shock failure life of 53 cycles. This extended service life could be attributed to the fact that the concave trapezoidal texture could effectively reduce the thermal stress and improve the thermal cycle life through the expansion and contraction of the interface. There is a significant difference in the coefficient of thermal expansion between the coating and the nickel based alloy substrate, and the coating experiences significant thermal mismatch stress at the interface after being subjected to thermal shock, which promotes crack initiation. As demonstrated in this study, surface texture played a key role in enhancing the interfacial strength and toughness of coatings. Notably, concave textures excelled in this regard due to their superior deflection toughening mechanism and anchoring effect. Together, these properties hindered crack growth and enhanced the bond between the coating and the substrate. Coatings with concave textures therefore exhibited three main failure modes:edge and trough locations due to normal compressive stress, and debonding failure at the interface. The interior of the coating on both sides of the concave structure was subject to tensile stress due to thermal mismatch, forming vertical cracks, that was, fracture failure. The ceramic layers between the concave structures buckled due to compressive stress. Through a comprehensive analysis of residual thermal stress and thermal shock testing, supplemented by energy release rate criteria, the research displays that concave trapezoidal texture as the best performer. This texture embodies the most powerful flexural toughening mechanism and interfacial toughening effect, effectively hinders crack propagation, delays fracture failure, and significantly enhances thermal shock resistance. Therefore, this study provides theoretical guidance for the design of thermal barrier coating surface textures, thereby contributing to the advancement of research and development of high-temperature components of aero-engines and steam turbines. |
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