Oxidation of minor elements from an iron-nickel-chromium-cobalt-phosphorus alloy in 17.3% CO 2-H 2 gas mixtures at 700-1000 °c

Dante Lauretta, Britney E. Schmidt

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Abstract

Fe-Ni-Cr-Co-P alloys were exposed to 17.3% CO 2-H 2 gas mixtures to investigate the oxidation of minor elements in metallic alloys in the early solar system. Reaction temperatures varied between 700 and 1000 °C. Gas-phase equilibrium was attained at 800, 900, and 1000 °C, yielding H 2-H 2O-CO-CO 2 gas mixtures. Experiments at 700 and 750 °C did not achieve gas-phase equilibrium and were performed in H 2-CO 2 gas mixtures. Reaction timescales varied from 1 to 742 h. The experimental samples were characterized using optical microscopy, electron microprobe analysis, wavelength-dispersive- spectroscopy X-ray elemental mapping, and X-ray diffraction. In all experiments Cr experiences internal oxidation to produce inclusions of chromite (FeCr 2O 4) and eskolaite (Cr 2O 3) and surface layers of Cr-bearing magnetite [(Fe,Cr) 3O 4]. At 900 and 1000 °C, P is lost from the alloy via diffusion and sublimation from the metal surface. Analysis of P zoning profiles in the remnant metal cores allows for the determination of the P diffusion coefficient in the bulk metal, which is constant, and the internally oxidized layer, which is shown to vary linearly with distance from the metal surface. At 800 and 900 °C, P oxidizes to form a surface layer of graftonite [Fe 3(PO 4) 2] while at 700 and 750 °C P forms inclusions of the phosphide-mineral schreibersite [(Fe,Ni) 3P].

Original languageEnglish (US)
Pages (from-to)219-235
Number of pages17
JournalOxidation of Metals
Volume71
Issue number3-4
DOIs
Publication statusPublished - Apr 2009

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Keywords

  • Chromite (FeCr O )
  • Eskolaite (Cr O )
  • Fe-Ni-Cr-Co-P alloy
  • Graftonite (Fe [PO ] )
  • Magnetite (Fe O )
  • Oxidation
  • Schreibersite ([Fe,Ni] P)

ASJC Scopus subject areas

  • Inorganic Chemistry
  • Materials Chemistry
  • Metals and Alloys

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