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Correlation Between Microstructure and Mechanical Properties of Wirearc Additively Manufactured 310 Austenitic Stainless Steel

Rahimi, Ali | 2025

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 58273 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Pouranvari, Majid
  7. Abstract:
  8. Austenitic stainless steels are extensively used in high-temperature and corrosive environments due to their excellent corrosion resistance and mechanical stability. However, their single-phase austenitic structure makes them susceptible to solidification cracking (SC) during solidification and ductility dip cracking (DDC) in the intermediate temperature range (~700–1100 °C), which significantly limits their weldability and additive manufacturability. In this study, the mechanical behavior of WAAM-fabricated AISI 310 stainless steel was investigated at room temperature under various processing strategies. Using 1.2 mm diameter filler metal and 99.99% pure argon shielding gas, it was shown that the GMAW-based WAAM process induced DDC during thermal cycling, leading to a reduction in elongation along the X-direction to 39%. Replacing GMAW with Cold Metal Transfer (CMT) significantly decreased thermal stresses and increased delta ferrite formation in interdendritic and grain boundary regions, which in turn reduced microcrack density and improved room-temperature elongation to 47% along the X-direction. Further improvements were achieved through the application of a reciprocating deposition path, which increased grain boundary density and led to more uniform strain distribution. This strategy enhanced the ductility, increasing elongation from 39% to 47% in the X-direction and from 46% to 57% in the Z-direction. However, the presence of delta ferrite was found to locally limit ductility. A post-deposition heat treatment at 1150 °C resulted in complete recrystallization, twin formation, and the elimination of delta ferrite, which remarkably improved mechanical properties, with elongations reaching 57% and 71% along the X and Z directions, respectively. Additionally, implementing active water cooling during the WAAM process not only reduced thermal gradients and mechanical anisotropy but also enhanced the recrystallization response during subsequent heat treatment. These findings highlight the critical role of process control, thermal management, and post-processing in mitigating cracking phenomena and enhancing the mechanical performance of austenitic stainless steels in wire arc additive manufacturing
  9. Keywords:
  10. Austenitic Stainless Steel ; Wire and Arc Additive Manufacturing ; Additive Manufacturing ; Ductility-Dip Cracking ; Solidification Cracking Modeling ; Anisotropy ; Recrystallization ; Cold Metal Transfer (CMT)Welding

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