Internal-nitriding behavior of Ni-V and Ni-3Nb alloys

Journal Article · Mon Feb 01 04:00:00 EST 1999 · Oxidation of Metals

DOI:https://doi.org/10.1023/A:1018845901165· OSTI ID:335257

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, and Ni-3Nb alloys (w/o) were nitrided in 10 v/o NH{sub 3} (bal H{sub 2}) over the range of 700--1000 C. The growth rates of the reaction zones followed parabolic behavior for all of the alloys from 700 to 900 C. At 1000 C, Ni-2V and Ni-3Nb formed nitride scales, whereas Ni-5V and Ni-12V formed internal-nitride zones. Nitridation rates decreased with increasing vanadium content for the Ni-V alloys. VN precipitated in the Ni-V alloys and NbN precipitated in Ni-3Nb for all exposure conditions in which internal nitridation occurred. The precipitate morphology changed with temperature and distance from the gas-metal surface. The VN and NbN precipitates were generally small and spheroidal near the surface, increasing in size with distance and temperature. The NbN precipitates became Widmanstaetten at higher temperatures and/or increasing distance within the nitrided zone. The solubility of nitrogen in pure Ni was determined and found to decrease with increasing temperature from 700 to 1000 C. Expressions for the diffusion coefficient of nitrogen in nickel were determined from the measured permeabilities of each alloy and the nitrogen solubilities in nickel.

• OSTI ID: 335257
• Journal Information: Oxidation of Metals, Journal Name: Oxidation of Metals Journal Issue: 1-2 Vol. 51; ISSN OXMEAF; ISSN 0030-770X
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CHEMICAL COMPOSITION
MORPHOLOGY
NICKEL ALLOYS
NIOBIUM ALLOYS
NITRIDATION
PRECIPITATION
SOLUBILITY
TEMPERATURE DEPENDENCE
VANADIUM ALLOYS