Oxidation Behavior Of Cr2N, CrNbN, and CrTaN Phase Mixtures Formed on Nitrided Cr And Laves-Reinforced Cr Alloys
- ORNL
A series of single-phase Cr(X), single phase Cr{sub 2}X Laves phase, and two-phase Cr(X) + Cr{sub 2} X alloys (X = Nb or Ta) were thermally nitrided for 24 hr at 1100 C in N{sub 2}-4H{sub 2} and then oxidized for 2 hr at 1100 C in air. The Cr(X) phase nitrided to form Cr{sub 2}N while the Cr{sub 2}X phases nitrided to form a complex local mixture of Cr{sub 2}N/Cr and CrNbN/CrTaN, Cr{sub 3}Nb{sub 3}N/Cr{sub 3}Ta{sub 3}N phases depending on the depth in the nitrided zone. The Ta only slightly increased the isothermal oxidation rate of nitrided Cr(Ta) and Cr{sub 2}Ta-reinforced Cr alloys, compared with nitrided, unalloyed Cr. Further, the nitrided two-phase alloys Cr-9.5Ta and Cr-20Ta exhibited improved Cr{sub 2}O{sub 3} scale adherence relative to nitrided unalloyed Cr and Cr-1Ta. In contrast, Nb was detrimental to the oxidation resistance of the nitrided Cr(Nb) and Cr{sub 2}Nb-reinforced Cr alloys, resulting in the formation of nonprotective Cr-Nb oxides rather than continuous Cr{sub 2}O{sub 3}. A phenomenological explanation for these effects based on phase chemistry and microstructural distribution is presented. Implications of these results for understanding the oxidation behavior of developmental high-temperature, Laves-strengthened Cr alloys, as well as possible applications as oxidation and wear-resistant coatings are discussed.
- Research Organization:
- Oak Ridge National Laboratory (ORNL); High Temperature Materials Laboratory; Shared Research Equipment Collaborative Research Center
- Sponsoring Organization:
- FE USDOE - Office of Fossil Energy (FE)
- DOE Contract Number:
- AC05-00OR22725
- OSTI ID:
- 1003131
- Journal Information:
- Oxidation of Metals, Journal Name: Oxidation of Metals Journal Issue: 5/6 Vol. 61; ISSN 0030-770X
- Country of Publication:
- United States
- Language:
- English
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