Thermochemical post-processing of additively manufactured austenitic stainless steel

Cecilie V. Funch*, Kinga Somlo, Thomas L. Christiansen, Marcel A.J. Somers

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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Abstract

The effects of different thermochemical post-processing treatments on the microstructure and properties of additively manufactured austenitic stainless steel were investigated. If the nitrogen content in the as-built condition is high, austenitization in vacuum causes a reduction in nitrogen content near the surface. This can be remedied by applying a small amount of nitrogen in the gas during austenitization. Using high temperature solution nitriding, the surface hardness could be effectively raised by deliberate nitrogen ingress, while maintaining a very fine structure inside the primary austenite grains. The excellent combination of strength and ductility of the as-built condition is accompanied by a low degree of work-hardening. This condition showed elastic and plastic anisotropy. The vertically built condition exhibits a lower strength and an early initiation of yielding as compared to the horizontally built conditions. High temperature treatments were able to efficiently reduce the mechanical anisotropy exhibited in the as-built condition. A combination of high- and low temperature surface hardening was investigated using nitriding, carburizing and nitrocarburizing. In all cases expanded austenite developed on the surface, which created a strong hardness increase.
Original languageEnglish
Article number128495
JournalSurface and Coatings Technology
Volume441
Number of pages14
ISSN0257-8972
DOIs
Publication statusPublished - 2022

Keywords

  • Additive manufacturing
  • austenitic stainless steel
  • High temperature solution nitriding
  • Low temperature surface hardening
  • Thermochemical surface treatment
  • Microstructure characterization
  • Mechanical anisotropy

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