Oxidation behavior of Cr2N, CrNbN, and CrTaN phase mixtures formed on nitrided Cr and Laves-reinforced Cr alloys

被引:24
作者
Brady, MP [1 ]
Tortorelli, PF [1 ]
Payzant, EA [1 ]
Walker, LR [1 ]
机构
[1] Oak Ridge Natl Lab, Oak Ridge, TN 37831 USA
来源
OXIDATION OF METALS | 2004年 / 61卷 / 5-6期
关键词
oxidation; nitridation; Cr; nitride; laves; wear;
D O I
10.1023/B:OXID.0000032330.95411.ec
中图分类号
TF [冶金工业];
学科分类号
0806 ;
摘要
A series of single-phase Cr(X), single phase Cr2X Laves phase, and two-phase Cr(X) + Cr2X alloys (X = Nb or Ta) were thermally nitrided for 24 hr at 1100degreesC in N-2 - 4H(2) and then oxidized for 2 hr at 1100degreesC in air. The Cr(X) phase nitrided to form Cr2N while the Cr2X phases nitrided to form a complex local mixture of Cr2N/Cr and CrNbN/CrTaN, Cr3Nb3N/Cr3Ta3N phases depending on the depth in the nitrided zone. The Ta only slightly increased the isothermal oxidation rate of nitrided Cr(Ta) and Cr2Ta-reinforced Cr alloys, compared with nitrided, unalloyed Cr. Further, the nitrided two-phase alloys Cr-9.5Ta and Cr-20Ta exhibited improved Cr2O3 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 Cr2Nb-reinforced Cr alloys, resulting in the formation of nonprotective Cr - Nb oxides rather than continuous Cr2O3. 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.
引用
收藏
页码:379 / 401
页数:23
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