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Microstructural Study Of Inconel 718 Alloy Produced by VAR and Comparing it with Other Rapid Solidification Methods

Elyaszadeh, Idin | 2016

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 48439 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Ashuri, Hossein
  7. Abstract:
  8. The purpose of this investigation was to study the microstructure of the Inconel718 alloy wich was produced by VAR and suction casting method, and study the effect of cooling rate on the solidification structure of Inconel718 alloy. In the first a labratoary scale VAR furnace was made. After producing some sample's with this furnace, a suction casting sample was produced using a 3mm diameter copper mold. Metallography, SEM, EDS, and microhardness analysis was carried away. Cooling rate evaluation was done by using a equation between secondary dendrite arm spacing and solidification time. Results showed that by increasing cooling rate from 63 c/s to around 2000 c/s, columnar and equiaxed dendritic structure turns into a cell like form structure, primary dendrite arm spacing and Nb content in the interdendritic phase decreases and in the cell like form structure no Nb segregation was measured. It seems that in the cell like form structure, a diffusionless transformation has taken place. In the suction casting sample in the midradius area some quadgranular phase with high content of Nb and Ti and with 1097 vickers microhardness was seen. Microhardness increased with increasing cooling rate due to increase in Nb content in austenite phase as a solid solution element
  9. Keywords:
  10. Rapid Solidification ; Suction Caisson ; Microstructural Study ; Inconel 718 Nickel Based Superalloy ; Vacuum Arc Re-Melting ; Electroslag Refining

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