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Role of Base Metal Composition in Isothermal Solidification Time During Diffusion Brazing of Nickelbased Superalloys

Mohammad Kamal, Helia | 2020

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 52895 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Pouranvari, Majid
  7. Abstract:
  8. The nickel-based superalloys play a key role in the development of aircraft and power-generation turbines due to their exceptional properties of high temperature strength, toughness, crack growth resistance and resistance to degradation corrosive and oxidisation environment.In this thesis, the role of base metal composition in isothermal solidification time during diffusion brazing of Nickel-based super alloys was investigated. To achieve this aim, four different super alloys Hynes230, Hastalloy X, Nimonic 263 and Monel were used in similar joining systems. Systems of H230/H230, HX/HX, C263/C263, and Monel/Monel were joined by BNi2 interlayer at 1323K and for different times, until the isothermal solidification was completed in all systems. Solidification behavior of BNi2 interlayer before the completion of isothermal solidification in four systems was studied and the effect of joining time on isothermal solidification was discussed.The results showed that the composition of the nickel-based superalloys plays a strong role in determining the required time for obtaining intermetallic-free joint during diffusion brazing with the increase of boride-forming elements in the base superalloy which promotes in situ boride precipitation at the diffusion-affected zone can accelerate the diffusion flux of the boron into the base superalloy, leading to faster isothermal solidification. The higher the Cr+Mo+Nb+Ta+W content in base superalloy, the shorter the isothermal solidification time
  9. Keywords:
  10. Microstructure ; Nimonic C263 Superalloy ; Hastelloy X Superalloy ; Transient Liquid Phase Boneling (TLPB) ; Isothermal Solidification ; Hynes 230 Superalloy

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