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The effect of Cobalt Replacement by Nickel on Microstructure, Physical and Mechanical Properties of WC-Co Hardmetals

Muhammadpour, Meysam | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 41149 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Pourazerang, Kazem; Abachi, Parvin
  7. Abstract:
  8. WC-Co hardmetals that are produced through powder metallurgy rout are vastely used as wear resistant parts. In these materials hard particles of wolfram carbide are embodied in a cobalt binder. Because of their high hardness and adequate toughness, hardmetals have found wide range of applications in cutting tool industry. During the last decades a number of researches have been carried out to improve their mechanical and wear properties by different binders and carbide particle sizes. Because of high hardness, Tungsten carbide has a good wear resistant. It has very low thermal expansion coefficient and high wetting ability with molten metals. Unlike high hardness, it has limited toughness. One way to overcome this limitation is to combine WC with a more though material such as cobalt or nickel. Cobalt has excellent wetting and binding abilities and is used as binder phase in several cases. However WC-Co hardmetals have some technical problems; poor corrosion resistance, high cost and pollution of the environment are some of the cases. Subsituation of cobalt with other metals has always been figured out to improve their performance. Some metals that have been used as binder are iron, nickel and manganese. In addition to lower cost, nickel has higher corrosion resistance than cobalt. So it has higher wear resistance in corrosive and chemically aggressive conditions. Therefore, the mentioned problems can be solved by substitution of cobalt with nickel. In present work, gradual substitution of cobalt with nickel has been studied. This is supposed to make some alterations in mechanical and physical properties. Samples with different binder characteristics are prepared and magnetic saturation, coercive force, hardness and fracture toughness tests have been carried out. Then, indentation fracture toughness and metallographic evaluations have used to study mentioned samples. Finally, computational thermodynamics has been used to compare their behavior
  9. Keywords:
  10. Powder Metallurgy ; Nickel ; Cobalt ; Cemented Carbide ; Cerments ; Cutting Tools ; Hard Materials ; Computational Thermodynamics

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