The internal-nitriding behavior of Co-Fe-Al alloys

Journal Article · Fri Oct 01 04:00:00 EDT 1999 · Oxidation of Metals

DOI:https://doi.org/10.1023/A:1018835410193· OSTI ID:679198

Chen, I C ^[1]; Douglass, D L ^[2]

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1. Raytheon Systems Co., El Segundo, CA (United States). Sensors and Electronics Systems
2. Univ. of Arizona, Tucson, AZ (United States). Arizona Materials Labs.

Co-10Fe, Co-20Fe, and Co-40Fe alloys containing 3 at.% Al were internally nitrided in NH{sub 3}/H{sub 2} mixtures over the range 700--1000 C. The kinetics of thickening of the internal-reaction zone followed the parabolic rate law, suggesting that solid-state diffusion was rate controlling. Nitrogen permeabilities were obtained for each alloy. AlN was the only nitride to form for all materials and at all temperatures. At high temperature, the nitride precipitates formed hexagonal plates near the surface, the precipitates becoming more blocky near the reaction front. Precipitate size increased with increasing depth in the alloy and increasing temperature, because of competition between nucleation and growth processes. Increasing iron content increased the reaction kinetics due to increased nitrogen solubility with increasing iron content.

• OSTI ID: 679198
• Journal Information: Oxidation of Metals, Journal Name: Oxidation of Metals Journal Issue: 3-4 Vol. 52; ISSN OXMEAF; ISSN 0030-770X
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
AMMONIA
COBALT ALLOYS
HYDROGEN
IRON ALLOYS
KINETICS
NITRIDATION
PRECIPITATION
TEMPERATURE DEPENDENCE