Graded Si3N4 ceramics with hard surface and tough core by two-step hot pressing |
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| Affiliation: | 1. School of Electromechanical Engineering, Guangdong University of Technology, Guangzhou 510006, China;2. Department of Materials Science and Engineering, University of Sheffield, Sheffield S1 3JD, United Kingdom;1. State Key Lab of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China;2. School of Materials Science and Engineering, North University of China, Taiyuan 030051, China;3. School of Materials Science and Engineering, Dalian Jiaotong University, Dalian 116028, China;4. State Key Laboratory of Materials Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China;1. School of Electromechanical Engineering, Guangdong University of Technology, Waihuanxi Road, Guangzhou 510006, China;2. Department of Materials Science and Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD, UK;3. School of Materials Science and Engineering, South China University of Technology, Wushan Road, Guangzhou 510640, China |
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| Abstract: | Graded Si3N4 ceramics with hard surface and tough core were prepared by two-step hot pressing with the homogenous starting composition. The inner Si3N4 layer was firstly hot-pressed at 1800 °C, subsequently covered with Si3N4 powders on both sides, and finally hot-pressed at 1600 °C. After two-step hot pressing, the resulting ceramics exhibited a zoned microstructure, differentiated by the phase assemblage of Si3N4 and grain size. The outer layers were well bonded to the inner layer. The outer layer exhibited bimodal and fine-grained microstructure, whereas the inner layer exhibited bimodal and coarse-grained microstructure. Vickers hardness of outer and inner layers were 18.1±0.2 GPa and 16.0±0.2 GPa, respectively, and fracture toughness were 4.2±0.1 MPa m1/2 and 5.5±0.2 MPa m1/2, respectively. |
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| Keywords: | Graded ceramics Microstructure Hardness Toughness |
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