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| Effects of Heat Treatment Temperature on Microstructure and Interdiffusion Behavior of Thermal Barrier Coatings |
| Received:October 31, 2018 Revised:January 25, 2019 |
| View Full Text View/Add Comment Download reader |
| DOI：10.7643/ issn.1672-9242.2019.01.002 |
| KeyWord:thermal barrier coating heat treatment interdiffusion second reaction zone |
| Author | Institution |
| YANG Wen-hui |
Aviation Key Laboratory of Science and Technology on Advanced Corrosion and Protection for Aviation Material, AECC Beijing Institute of Aeronautical Materials, Beijing , China |
| MU Ren-de |
Aviation Key Laboratory of Science and Technology on Advanced Corrosion and Protection for Aviation Material, AECC Beijing Institute of Aeronautical Materials, Beijing , China |
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| Abstract: |
| Objective To improve the oxidation resistance and decrease the second reaction zone (SRZ) of thermal barrier coating (TBC). Methods The bond coating of HY5 (NiCoCrAlYHf) was prepared by vacuum arc ion plating on second genera-tion single crystal super-alloy DD32 to carry out vacuum diffusion treatment at 870 ℃ and 1000 ℃ respectively. And then YSZ was deposited on the bond coating by EB-PVD. Microstructure, composition and diffusion mechanism of the thermal barrier coating during high temperature cyclic oxidation were studied through test with SEM, EDS and EPMA. The inter diffusion co-efficient of Al element in 1, 125 h of oxidation was calculated. Results After thermal circulation at 1100 ℃, the absolute value of oxidation mass increment of the coating after thermal treatment at 1000 ℃ was small; the oxidation rate constant was 7.21× 10?4; and the cyclic oxidation resistance was good. For samples after thermal treatment at 1000 ℃, the distribution of Ni, Al, Cr and other elements was relatively uniform from the surface of the coating to the direction of the substrate; and the change of element content was relatively smooth at the interface between the coating and the substrate. For samples after thermal treatment at 870 ℃, the mass fraction of Ni and other elements was unevenly distributed; the element content changed abruptly at the interface between the coating and the substrate, resulting in a low degree of element homogenization. The diffusion coefficient of Al element increased with the increase of concentration. With the extension of oxidation time, the element diffusion between the bonding layer and the superalloy increased and the diffusion coefficient of Al element decreased. After 125 h of cyclic oxidation, the bonding coating / substrate interface had interdiffusion region. Local region of interdiffusion region was rich in Cr, but the Al content was low. After 250 h of cyclic oxidation, topologically dense phase TCP precipitated under the diffusion region of the thermal barrier coating sample, forming a secondary reaction zone (SRZ). For samples with vacuum diffusion temperature of 870 ℃, the secondary reaction zone was more obvious. Conclusion Vacuum heat treatment of metal bond coating at 1000 ℃ can effectively improve the oxidation resistance of the coating. The homogenization degree of elements in the coating is high, and the diffusion of Al element is slow. At the same time, the width of the diffusion region is small and the secondary reaction zone is not obvious. |
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