Investigation of the physical and mechanical properties of hot-pressed machinable Si3N4/h-BN composites and FGM |
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Authors: | Wang Ruigang Pan Wei Jiang Mengning Chen Jian Luo Yongming |
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Affiliation: | State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, People's Republic of China |
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Abstract: | A new design method of machinable ceramic composites was proposed, which applies the graded-structure concept to the design of machinable Si3N4 ceramics. Silicon nitride/hexagonal boron nitride (h-BN) ceramic composites and functionally graded materials were fabricated by hot pressing at 1750 °C for 2 h, varying the alignment of the amount of hexagonal BN using powder layering method. The improved machinability of Si3N4/h-BN composite can be attributed to addition of layered structure hexagonal BN. Hexagonal BN possesses excellent cleavage planes perpendicular to the c-axis. Ease of machining depends on degree of crystal interlocking; hence volume content of h-BN crystals and their aspect ratio affect machinability. The texture of h-BN and β-Si3N4 was observed during hot pressing sintering. Physical and mechanical properties of Si3N4/h-BN with different content of h-BN were investigated, such as bulk density, Vickers's hardness, flexural strength, and elastic modulus. All of these properties are important for the design of the machinable Si3N4/h-BN FGM (Functionally Graded Materials). |
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Keywords: | Si3N4/h-BN FGM Machinability |
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