Additive manufacturing of functionally graded transition joints between ferritic and austenitic alloys

J. S. Zuback, T. A. Palmer, T. DebRoy

Research output: Contribution to journalArticle

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Abstract

Dissimilar metal joints between ferritic and austenitic alloys are susceptible to premature failure due to diffusive carbon loss from the ferritic alloy driven by abrupt changes in carbon chemical potential. Compositional grading of transition joints fabricated using laser-based directed energy deposition additive manufacturing offers a means for limiting carbon diffusion. Here we fabricate functionally graded transition joints between a ferritic and austenitic alloy, characterize spatial variations of chemical composition, microstructure and hardness, and test their effectiveness to limit carbon loss from the ferritic alloy. Microstructural studies and carbon potential variations in the functionally graded material showed that the length of the joints can be shorter, and there is no benefit to continue compositional grading once the microstructure becomes fully austenitic. Since dissimilar joints have an expected lifetime of several decades, long service times were simulated through accelerated heat treatment experiments at elevated temperatures for both a dissimilar metal weld and a functionally graded transition joint. While the dissimilar weld showed pronounced carbon loss from the ferritic side, there was insignificant change in the carbon concentration profile in the functionally graded joint indicating effectiveness of the graded joints to perform under service conditions.

LanguageEnglish (US)
Pages995-1003
Number of pages9
JournalJournal of Alloys and Compounds
Volume770
DOIs
StatePublished - Jan 5 2019

Fingerprint

3D printers
Carbon
Dissimilar metals
Welds
Microstructure
Functionally graded materials
Chemical potential
Hardness
Heat treatment
Lasers

All Science Journal Classification (ASJC) codes

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

Cite this

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abstract = "Dissimilar metal joints between ferritic and austenitic alloys are susceptible to premature failure due to diffusive carbon loss from the ferritic alloy driven by abrupt changes in carbon chemical potential. Compositional grading of transition joints fabricated using laser-based directed energy deposition additive manufacturing offers a means for limiting carbon diffusion. Here we fabricate functionally graded transition joints between a ferritic and austenitic alloy, characterize spatial variations of chemical composition, microstructure and hardness, and test their effectiveness to limit carbon loss from the ferritic alloy. Microstructural studies and carbon potential variations in the functionally graded material showed that the length of the joints can be shorter, and there is no benefit to continue compositional grading once the microstructure becomes fully austenitic. Since dissimilar joints have an expected lifetime of several decades, long service times were simulated through accelerated heat treatment experiments at elevated temperatures for both a dissimilar metal weld and a functionally graded transition joint. While the dissimilar weld showed pronounced carbon loss from the ferritic side, there was insignificant change in the carbon concentration profile in the functionally graded joint indicating effectiveness of the graded joints to perform under service conditions.",
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Additive manufacturing of functionally graded transition joints between ferritic and austenitic alloys. / Zuback, J. S.; Palmer, T. A.; DebRoy, T.

In: Journal of Alloys and Compounds, Vol. 770, 05.01.2019, p. 995-1003.

Research output: Contribution to journalArticle

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