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Investigating Microstructure and Mechanical Properties of IN738 Nickel Base Superalloy Repaired by Wide Gap Activated Diffusion Brazing Method

Barzgaran, Vahid | 2025

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  1. Type of Document: Ph.D. Dissertation
  2. Language: English
  3. Document No: 58137 (57)
  4. University: Sharif University of Technology, International Campus, Kish Island
  5. Department: Science and Engineering
  6. Advisor(s): Ekrami, Ali Akbar
  7. Abstract:
  8. This study investigates the effects of filler and additive powder weight percentages on the microstructural and mechanical properties of IN738LC nickel-based superalloy repaired using the Wide Gap Activated Diffusion Brazing (WGB) method. The base metal powder, IN738LC, was combined with AMDRY BRB filler metal, and the brazing process was followed by diffusion heat treatment and aging cycles to optimize the microstructure and mechanical properties. Optical microscopy, scanning electron microscopy (SEM), and four-point bending tests were employed to evaluate the microstructure and mechanical performance of the brazed joints. The results indicate that a brazing temperature of 1180 °C for 30 minutes, followed by heat treatment at 1120 °C for 4 hours and aging at 850 °C for 24 hours, yielded the lowest porosity and eutectic phase formation in the brazed region. Samples with 40 wt% filler exhibited optimal mechanical properties at both ambient and elevated temperatures. Fractography revealed that crack initiation primarily occurred in the filler metal, highlighting the importance of microstructure control in achieving high-performance brazed joints
  9. Keywords:
  10. Wide Gap Diffusion Brazing ; Microstructure ; Mechanical Properties ; Fractography ; Activated Diffusion Brazing ; Inconel 738 Nickel Based Superalloy

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