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Effect of Remelting Processes on Microstructure and Segregation in Inconel-100 Superalloys Produced by VIM

Ahmadabadi, Morteza | 2016

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 49113 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Tavakkoli, Ruhollah
  7. Abstract:
  8. In the present work, the effect of different methods of melting, remelting and solidification conditions on the microstructural evolution of IN100 superalloy was investigated. For this purpose, the superalloy was solidified within steel and ceramic molds to provide different cooling rates. Furthermore, the re-melting processes using ESR in the water circulated copper mold and ceramic molds, VAR and combined ESR and VAR were considered. The microstructure of alloy under different casting and remelting conditions were studied by means of optical and SEM microscopy and ESD analysis. According to our results, the ingot which was cast in the ceramic molds, due to lower cooling rate during solidification, as a result more opportunities for Al and Ti diffusion, has lower fraction of γ/γ'eutectic phases. Because of potential the matrix was increased to form γ' phase, the microstructure of ingots that was solidified slowly has more γ' phase fractions in contrast to other ingots. The γ' phase has a significant role to improve the high-temperature properties of this alloy and by increasing the volume fraction of this phase, the creep resistance of alloy will be increased. Moreover, our results showed that lower cooling rate increased the volume fraction of secondary γ' phase. In addition to, ingots remelted by ESR in the copper molds, had less volume fraction of the (strengthening) γ' phase in their microstructure, compared to VAR ingots, because of more volume fraction of eutectic phases
  9. Keywords:
  10. Vacuum Arc Re-Melting ; Vacuum Induction Melting (VIM)Process ; IN100 Superalloy ; Emission Dispersive Analazer ; Electro Slag Remelting (ESR)

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