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Article Dans Une Revue Acta Materialia Année : 2019

Atomic-scale grain boundary engineering to overcome hot-cracking in additively-manufactured superalloys

Paraskevas Kontis
Edouard Chauvet
  • Fonction : Auteur
Zirong Peng
  • Fonction : Auteur
Junyang He
  • Fonction : Auteur
Alisson Kwiatowski Da Silva
  • Fonction : Auteur
Dierk Raabe
  • Fonction : Auteur
Cathrine Tassin
  • Fonction : Auteur
Jean-Jacques Blandin
  • Fonction : Auteur
Stéphane Abed
  • Fonction : Auteur
Rémy Dendievel
  • Fonction : Auteur
Baptiste Gault
  • Fonction : Auteur
  • PersonId : 1076009

Résumé

There are still debates regarding the mechanisms that lead to hot cracking in parts build by additive manufacturing (AM) of non-weldable nickel-based superalloys. This lack of in-depth understanding of the root causes of hot cracking is an impediment to designing engineering parts for safety-critical applications. Here, we deploy a near-atomic-scale approach to investigate the details of the compositional decoration of grain boundaries in the coarse-grained, columnar microstructure in parts built from a non-weldable nickel-based superalloy by selective electron-beam melting. The progressive enrichment in Cr, Mo and B at grain boundaries over the course of the AM-typical successive solidification and remelting events, accompanied by solid-state diffusion, causes grain boundary segregation induced liquation. This observation is consistent with thermodynamic calculations. We demonstrate that by adjusting build parameters to obtain a fine-grained equiaxed or a columnar microstructure with grain width smaller than 100 μm enables to avoid cracking, despite strong grain boundary segregation. We find that the spread of critical solutes to a higher total interfacial area, combined with lower thermal stresses, helps to suppress interfacial liquation.
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Dates et versions

hal-02556990 , version 1 (28-04-2020)

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Paraskevas Kontis, Edouard Chauvet, Zirong Peng, Junyang He, Alisson Kwiatowski Da Silva, et al.. Atomic-scale grain boundary engineering to overcome hot-cracking in additively-manufactured superalloys. Acta Materialia, 2019, ⟨10.1016/j.actamat.2019.07.041⟩. ⟨hal-02556990⟩
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