| HU Kaifei,WANG Peipei,SUN Wanchang,HOU Zhaoqi,YI Dawei,LUO Huan,REN Xuanru.Effect of Temperature on Oxidation Protection Performance and Mechanism of B4C Coating[J],53(4):89-97 |
| Effect of Temperature on Oxidation Protection Performance and Mechanism of B4C Coating |
| Received:December 21, 2022 Revised:March 18, 2023 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2024.04.008 |
| KeyWord:coating graphite boron carbide (B4C) glass film oxidation protection oxygen-blocking mechanism |
| Author | Institution |
| HU Kaifei |
College of Materials Science and Engineering, Xi'an University of Science & Technology, Xi'an , China |
| WANG Peipei |
College of Materials Science and Engineering, Xi'an University of Science & Technology, Xi'an , China |
| SUN Wanchang |
College of Materials Science and Engineering, Xi'an University of Science & Technology, Xi'an , China |
| HOU Zhaoqi |
College of Materials Science and Engineering, Xi'an University of Science & Technology, Xi'an , China |
| YI Dawei |
College of Materials Science and Engineering, Xi'an University of Science & Technology, Xi'an , China |
| LUO Huan |
College of Materials Science and Engineering, Xi'an University of Science & Technology, Xi'an , China |
| REN Xuanru |
Carbon Matrix Composites Research Institute, Henan Academy of Sciences, Zhengzhou , China |
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| Abstract: |
| The oxidation of B4C coatings can generate a B2O3 glass film, which is a good oxidation protection material for carbon materials. The effect of temperature on the oxidation protection performance and mechanism of B4C coatings was studied, and the optimal oxidation protection temperature range of B4C coatings and the evolution of oxidation protection mechanism of B4C coatings at different temperature were obtained. In this paper, a B4C coating was prepared on a graphite surface by spark plasma sintering (SPS), and its oxidation behavior and oxidation protection mechanism were investigated by isothermal oxidation at different temperature (800, 1 000, 1 200, 1 400 ℃) and dynamic oxidation in a wide temperature range from room temperature to 1 400 ℃. The phase composition, micro-morphology and oxygen diffusion of B4C coated graphite samples before and after oxidation were analyzed with an X-ray diffraction (XRD), a scanning electron microscopy (SEM) and an energy dispersive spectroscopy (EDS). The results showed that the B4C coating was oxidized at 800, 1 000, 1 200 and 1 400 ℃ for 100 min, the oxidation protection efficiency was 98.43%, 98.61%, 94.4% and 92.8%, respectively. When the B4C coating was oxidized at 800 ℃, the rate of coating oxidation and glass film formation were slow, so oxygen diffused to the interior of the coating and the substrate, resulting in rapid reduction of oxidation protection efficiency at the initial stage of oxidation; when continuous B2O3 glass was formed, the pores in the coating were reduced, and the protective efficiency of the coating rebounded; after oxidation for 60 min, the oxidation protection efficiency was basically stable. The B4C coating had better protection effect at the initial stage of oxidation at 1 000 ℃ than other temperature; with the duration of oxidation, its protection efficiency slowly decreased, and the oxidation protection efficiency was basically stable after oxidation for 60 min. The protection efficiency only decreased by 1.39% after oxidation for 100 min at 1 000 ℃. When B4C coated graphite samples were oxidized at 1 200 and 1 400 ℃, the oxidation protection efficiency of the B4C coating decreased rapidly with oxidation time; after oxidation for 100 min, the protection efficiency was 94.4% and 92.8%, respectively. The B4C coating had the best film-formation effect and the highest protection efficiency at 1 000 ℃. The B4C coated graphite sample was oxidized from room temperature to 1 400 ℃, and the mass first remained stable (<700 ℃), then increased rapidly (700-900 ℃), and finally increased slowly (>900 ℃). The protection efficiency of the B4C coating remained stable below 600 ℃, decreased slowly at 600-700 ℃, decreased rapidly at 700-800 ℃, rebounded rapidly at 800-900 ℃, remained basically stable at 900-1 100 ℃, and weakened slowly above 1 100 ℃. Combined with isothermal oxidation and wide temperature range oxidation, it can be concluded that the B4C coating has good oxidation protection effect in the temperature range of 800-1 100 ℃. The oxidation protection mechanism of the B4C coating below 800 ℃ is mainly structural oxygen-blocking; the protection mechanism changes from structural oxygen-blocking to inert oxygen-blocking at 800-900 ℃; and the protection mechanism is mainly inert oxygen-blocking above 900 ℃. When the temperature exceeds 1 100 ℃, the volatilization of glass film intensifies and the inert oxygen-blocking weakens. |
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