Joining of SiC ceramics using the Ni-Mo filler alloy for heat exchanger applications |
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| Affiliation: | 1. State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, 200050, China;2. Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, 100049, China;3. State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin, 150001, China;4. School of Material and Engineering, Shanghai University, Shanghai, 200444, China;1. School of Materials Science and Engineering, Yeungnam University, 38541, South Korea;2. Engineering Laboratory of Nuclear Energy Materials, NIMTE, Chinese Academy of Sciences, 315201, China;1. School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009, China;2. Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, China;1. State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin, 150001, China;2. AECC Shenyang Liming Aero-Engine Co., Ltd, Shenyang, 110043, China;3. Institute for Advanced Ceramics, School of Materials Science and Engineering, Harbin Institute of Technology, Harbin, 150080, China;4. State Key Laboratory of Advanced Brazing Filler Metals and Technology, Zhengzhou Research Institute of Mechanical Engineering, Zhengzhou, 450001, China;5. Army Academy of Armored Forces, Changchun, 130117, China |
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| Abstract: | In order to meet the sealing demands of SiC heat exchanger, the Ni-Mo filler alloy was designed, prepared and employed to braze SiC ceramics. Wetting behavior of the Ni-Mo filler alloy on SiC ceramics and interfacial microstructure of the brazed joints were systematically characterized using optical observation furnace and XRD, SEM, EDS, TEM, respectively. Flexural strengths of the brazed joints at room temperature and high temperature were measured with four-point flexural strength method. HCl immersion test was performed to evaluate the corrosion resistance of the joints. The Ni-Mo filler alloy exhibited excellent wettability on SiC ceramics. During the process of brazing, SiC reacted with element Ni of the Ni-Mo filler alloy, resulting in the formation of Ni2Si + graphite reaction layer adjacent to the SiC substrate. Ni3Mo3C and Ni2Si compounds were precipitated at the center of brazing seam. When the brazing temperature increased from 1250 ℃ to 1400 ℃, the thickness of Ni2Si + graphite layer increased gradually. The maximum room-temperature flexural strength of 174 ± 33 MPa was obtained when brazed at 1300 ℃ for 40 min. The joints also exhibited stable high-temperature strength and acid corrosion resistance. When the test temperature was 700 ℃, 800 ℃, 900 ℃, the joints gave the strength retention rate of 92.5 %, 79.8 %, 67.2 %, respectively. It was believed that the formation of high melting point phases played an important role. Residual strength of the joints after HCl corrosion exceeded 130 MPa, revealing a good potential for applications in corrosion environment. |
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| Keywords: | SiC ceramic Joining Ni-Mo filler alloy Flexural strength Corrosion resistance |
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