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Effect of Nitrogen Addition on the Microstructure and Mechanical Properties of a Pearlitic Matrix Gray Cast Iron

Kamoori Yousefabad, Elham | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42449 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Davami, Parviz
  7. Abstract:
  8. Gray Cast Irons are the most important engineering Cast Irons. Gray color of fracture surface and morphology of graphite flakes are the reasons of this naming. Gray iron is relatively cheap with easy production; because of wide chemical composition range rather other cast irons. Furthermore, shrinkage and feeding in the casts from gray iron, besides surface finishing by machining are easy. The other properties of gray iron are resistance against sliding wear, high thermal conduction coefficient, low module of elasticity and thermally shock resistance. In this research, the effects of added nitrogen as an alloying element and cooling rate on microstructure, hardness and tensile properties of pearlitic matrix gray iron castings are investigated. The samples with four nitrogen content along with three cooling rates are used for this study. Atomic emission spectroscopy by quanto-meter equipment has been used for chemical composition analysis. Stereo microscopy, optical microscopy and scanning electron microscopy (SEM) were utilized for evolution of different aspects of sample's structure and microstructure. Brinell hardness and tensile properties of the samples were examined as mechanical properties. Addition of nitrogen and the rise of cooling rate of castings results in decrease of type A graphite flakes size, increase of hardness and ultimate tensile strength (UTS). It should be noted that, the UTS increase is more evidence when cooling rate is decreased, because of increasing of nitrogen reaction time in the structure
  9. Keywords:
  10. Gray Cast Iron ; Casting ; Microstructure ; Mechanical Properties ; Cooling Rate ; Nitrogen Addition

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