Internal-carburizing behavior of Ni-V, Ni-Cr, and Ni-3Nb alloys

Journal Article · Thu Apr 01 04:00:00 EST 1999 · Oxidation of Metals

DOI:https://doi.org/10.1023/A:1018814521638· OSTI ID:351476

Allen, A T ^[1]; Douglass, D L ^[2]

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1. Metals Technology, Inc., Northridge, CA (United States)
2. Univ. of Arizona, Tucson, AZ (United States). Arizona Materials Lab.

Ni-2V, Ni-5V, Ni-12V, Ni-10Cr, Ni-20Cr, and Ni-3Nb alloys were carburized in 1.5 v/o C{sub 3}H{sub 6} (bal H{sub 2}) over the range 700--1000 C. Carburization of Ni-5V, Ni-12V, NI-20Cr, and Ni-3Nb obeyed the parabolic rate law. Ni-2V and Ni-10Cr, however, formed only thin carbide scales upon carburizing. Carburization rates decreased with increased vanadium content from Ni-5V to Ni-12V for all exposure conditions. V{sub 4}C{sub 3} formed throughout the reaction zones of Ni-12V. Cr{sub 3}C{sub 2} formed in the surface regions and Cr{sub 7}C{sub 3} formed within the interior of Ni-20Cr. NbC precipitated in Ni-3Nb under all conditions. The precipitate morphology changed with temperature and distance from the gas-metal surface. V{sub 4}C{sub 3} and Cr{sub 3}C{sub 2} particles were generally small and spheroidal near the surface of Ni-12V and Ni-20Cr, respectively, increasing slightly in size with distance from the surface and with increasing temperature. The vanadium and chromium carbides formed intergranular networks toward the reaction fronts. The NbC precipitates were generally large and became Widmanstaetten at increasing distance within the carburized zone of Ni-3Nb. Expressions for the diffusion coefficient of carbon in nickel from the measured permeabilities and carbon solubility data were determined. Solubility products were determined for all of the carbides formed and found to be large in comparison with the product of the activities of the precipitate elements. Wagner`s theory of internal oxidation was shown to be an approximation to the carburization kinetics at temperatures of 900 C or higher.

• OSTI ID: 351476
• Journal Information: Oxidation of Metals, Journal Name: Oxidation of Metals Journal Issue: 3-4 Vol. 51; ISSN OXMEAF; ISSN 0030-770X
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CARBIDES
CARBURIZATION
CHROMIUM ALLOYS
KINETICS
MICROSTRUCTURE
MORPHOLOGY
NICKEL ALLOYS
NIOBIUM ALLOYS
PRECIPITATION
VANADIUM ALLOYS