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Formation of ZrC-WC-W Composites Ceramics by DCP Method and Investigation of Their Physical Properties, Phase Composition and Microstructure

Davarpanah, Amin | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42757 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Faghihi Sani, Mohammad Ali; Mirhabibi, Ali Reza
  7. Abstract:
  8. Refractory metals (W,Re,Ta,Mo,Nb) and their alloys can exhibit exceptional properties at elevated temperatures. However, refectory metals tend to be relatively heavy and, in some cases, can be relatively difficult to form in complex shapes at low cost. Light composites of refractory metals with high-melting ceramics, which can be fabricated into dense, near net shapes at low temperatures, would be particularly attractive for advanced aerospace applications. In this project, WC powders have been pressed and shaped to cylindrical preforms. Secondly, these performs have been sintered slightly(presintered) into porous, rigid ones with about 50% open porosity. Finally, in order to reach dense ZrC-WC-W composites, the performs have been infilterated with molten Zr-Cu alloy. In accordance to the reaction between zirconium in the alloy and WC perform, ZrC phase was prodeuced and the pores were filled with the products because of the volume increase induced by the reaction. Composite composition and its properties such as final density has been investigated by changing composition of initial perform and size distribution of initial WC powders. In order to study the results, complimentary analysises such as X-ray Spectrometry, Scaninig Electron Microscopy, hardness measurement and thermal analysis have been performed. According to the results, 2 hours is the adequate time for complete reaction to take place and deired amount of phases have been produced in this method. Adding milled WC powders to the initial preform has improved WC consumption during the reaction, so W and ZrC content of final composite have been increased.
  9. Keywords:
  10. Tungsten Carbide ; Displacive Compensation of Porosity (DCP) ; Metal-Ceramic Composite ; Zirconium Carbide ; Zirconium-Copper Alloy

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