Fractography of silicon nitride based ceramics to guide process improvements |
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| Affiliation: | 1. Department of Materials Science, Montanuniversitaet Leoben, Franz Josef Straße 18, A-8700 Leoben, Austria;2. Materials Center Leoben Forschung GmbH, Roseggerstrasse 12, A-8700 Leoben, Austria;1. Jozef Stefan Institute, Jamova 39, Ljubljana, Slovenia;2. VALL-CER d.o.o., Ljubljana, Slovenia;1. Institute of Physics of Materials, Czech Academy of Sciences, ?i?kova 513/22, 616 62 Brno, Czech Republic;2. Research Centre UNIZA, University of ?ilina, Univerzitná 8215/1, 010 08 ?ilina, Slovakia;3. Institute of Rock Structure and Mechanics, Czech Academy of Sciences, V Hole?ovi?kách 41, 180 00 Prague, Czech Republic;4. Institute of Macromolecular Chemistry, Czech Academy of Sciences, Heyrovského nám. 2, 162 06 Prague, Czech Republic;1. State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, China;2. University of Chinese Academy of Sciences, Beijing, China;1. State Key Laboratory of Coal Mine Disaster Dynamics and Control, College of Aerospace Engineering, Chongqing University, Chongqing 400030, China;2. Chongqing Key Laboratory of Nano-Micro Composite Materials and Devices, School of Metallurgy and Materials Engineering, Chongqing University of Science and Technology, Chongqing 401331, China;3. Chongqing Nankai Secondary School, Chongqing 400030, China |
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| Abstract: | Fractography is an important tool to understand and identify the cause of the failure in materials. This understanding can be used to make changes in raw materials selection and processing to increase the strength of brittle materials. This study reports the fracture behavior of hot-pressed silicon nitride based ceramics, with focus on dominant flaw identification with respect to material and process parameters. Silicon nitride is an important material for structural applications which require high strength and wear resistance, such as bearings, nozzles, and cutting tools. Silicon nitride with a target base composition of Si6-zAlzOzN8-z (z = 0.5), along with varying boron dopant levels, was explored in this work. Detailed fractographic analyses revealed that the majority of fracture origins were internal flaws due to the foreign impurities introduced at various stages of processing. All materials were found to have reasonably high strength (800?1100 MPa). Strength was inversely proportional to the square root of the flaw size, however no correlation was found between measured flexural strength and fracture origin types. Mirror constants calculated from fracture mirror measurements ranged between 5.8 and 9.8 MPa.m1/2. |
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| Keywords: | Silicon nitride Fracture mirror Flexural test Flaws |
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