| LIU Qi,SANG Ke-zheng,ZENG De-jun.Preparation and Structure of WC+W2C Coating on Porous SiC Surface[J],51(3):226-233 |
| Preparation and Structure of WC+W2C Coating on Porous SiC Surface |
| Received:September 26, 2021 Revised:December 30, 2021 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2022.03.024 |
| KeyWord:wettability sol-gel silicon carbide coating WC+W2C |
| Author | Institution |
| LIU Qi |
School of Materials Science and Engineering, Chang'an University, Xi'an , China |
| SANG Ke-zheng |
School of Materials Science and Engineering, Chang'an University, Xi'an , China |
| ZENG De-jun |
School of Materials Science and Engineering, Chang'an University, Xi'an , China |
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| Abstract: |
| To improve the wettability of the metal with SiC and to avoid damage to the porous SiC substrate during the infiltration process. A certain amount of SiC powder was mixed with about 5wt.% alcohol-soluble phenolic resin. Then, the ϕ15 mm×4 mm specimens were obtained by cold pressing with 84 MPa press for 1 min. Finally, porous SiC substrates were prepared by oxidation sintering. The raw materials were prepared according to the mass ratio of ammonium metatungstate, citric acid, ethylene glycol and water-soluble phenolic resin 6:3:2:0.84. By adjusting the heating time to control the evaporation of solvent deionized water, the molar ratio of W to C is 1:2 and the solid content of ammonium metatungstate is 50%. One side of sintered porous SiC ceramic sample is immersed in the sol, and the pore of SiC ceramic was automatically impregnated with the sol by capillary force. When the surface of SiC ceramic sol exudated, took out the sample and filter paper to scrape off the surface of excess sol, and then dried. Finally, the sample was placed in a tubular furnace to begin hydrogen reduction. Samples with WO3 layer were obtained by heating them to 500 ℃ at a heating rate of 10 ℃/min for 3 h. Then it was heated to 800, 900, 1000, 1100 and 1350 ℃ at a heating rate of 10 ℃/min for 3 h (among which, 1 h, 2 h and 3 h were set at 900 ℃), and WC+W2C coating was obtained. In addition, WC+W2C coatings could be obtained on the porous SiC surface by the sol-gel hydrogen reduction method at 900 ℃. The structure and composition of the coating, the effects of heat treatment temperature and time as well as the times of suction of the sol on it, were studied by X-ray diffractometry and scanning electron microscopy. The results showed that W and C could react and form WC and W2C when the heat treatment temperature was between 900 ℃ and 1100 ℃, but the coating reacted with the substrate and the WSi2 compound appeared when the temperature was increased to 1350 ℃. With the increase of heat treatment time at 900 ℃, the coating particles gradually gathered and grew, and the distance between coating particles became larger. With the increase of suction times, the number and the average size of the particles after reduction increased. By 5 times of suction of sol, the percentage of surface area occupied by the coating particles reached saturation, which was about 40%. The average particle size of the coating particles reached 0.53 μm by 6 times of suction. It can be concluded that coating is formed by WC+W2C, which appeared as particles and distributes on the porous SiC substrate. The number of the particles and the percentage of area occupied can be effectively increased by increasing the number of sol suction to 6 times. The best technological condition based on the wetting effect of coating and metal is that the sample is treated at 900 ℃ for 1 hour after suctioning the sol by 6 times. |
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