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Development of High Entropy Alloys Filler Metal for Brazing of Haynes230 Solid Solution Nickel Based Superalloy

Azghani, Navid | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 58106 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Pouranvari, Majid; Tavakoli, Rouhollah
  7. Abstract:
  8. Diffusion brazing is a key process in manufacturing and repairing of nickel-based superalloys. Using common filler metals which contain melting point depressant elements like boron, silicon and phosphorus leads to formation of brittle intermetallics in the joining area. In spite of removing these undesired phases in diffusion brazing due to completion of the isothermal solidification, this process needs long period of time, especially in wide gap joints. Initially in this study, one specimen of Haynes230 superalloy was diffusion brazed with MBF80 filler metal and the mentioned problems was exhibited. In order to overcome these obstacles, a high entropy alloy (HEA) filler metal with composition of Mn40Cu20Ni18Co10Cr7Fe5 was developed for brazing of Haynes230. Design of this HEA was based on the main parameters of high entropy alloy families emphasizing the lowest possible melting point and solid solution microstructure. Afterwards, some joints were made at the temperature of 1180 °C which is enough for melting and overheating of HEA filler metal and also is in the range of Haynes230 solution treatment temperature. Metallurgical evolution of joints depends on interdiffusion of base metal and filler metal’s elements especially Mn, Cu, Cr and W. Microstructural investigation of joints shows the solution and growth of tungsten and chromium carbides occur in diffusion affected zone of joints. Moreover, these carbides and Manganese rich phases can be created in the center of joints. By selecting appropriate parameters for diffusion brazing, mainly temperature and time of brazing, a good wide gap joint free of harmful intermetallic compounds and carbides, with a microhardness profile similar to base metal can be achieved in a short time in comparison with common filler metals like MBF80
  9. Keywords:
  10. High Entropy Filler Alloy ; Hynes 230 Superalloy ; Hard Brazing ; Wide Gap Diffusion Brazing ; Nickel-Base Superalloy

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