Internal-Nitriding Behavior of Ni-V and Ni-3NbAlloys

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• 作者：Allen ; A. T. ; Douglass ; D. L.
• 关键词：INTERNAL NITRIDING ; Ni ; V ALLOYS ; Ni ; Nb ALLOYS ; NITROGEN SOLUBILITIES ; PRECIPITATE MORPHOLOGIES
• 刊名：Oxidation of Metals
• 出版年：1999
• 出版时间：1999
• 年：1999
• 卷：51
• 期：1/2
• 页码：1-22
• 全文大小：576 KB

文摘

Ni-2V, Ni-5V, Ni-12V, and Ni-3Nb alloys (w/o)were nitrided in 10 v/o NH$\_3$(bal.H$\_2$) over the range of 700-1000°C. Thegrowth rates of the reaction zones followed parabolicbehavior for all of the alloys from 700 to 900°C. At 1000°C, Ni-2V andNi-3Nb formed nitride scales, whereas Ni-5V and Ni12Vformed internal-nitride zones. Nitridation ratesdecreased with increasing vanadium content for the Ni-Valloys. VN precipitated in the Ni-V alloys and NbNprecipitated in Ni-3Nb for all exposure conditions inwhich internal nitridation occurred. The precipitatemorphology changed with temperature and distance from the gas-metal surface. The VN and NbNprecipitates were generally small and spheroidal nearthe surface, increasing in size with distance andtemperature. The NbN precipitates became Widmanstattenat higher temperatures and/or increasing distance withinthe nitrided zone. The solubility of nitrogen in pure Niwas determined and found to decrease with increasingtemperature from 700 to 1000°C. Expressions for the diffusion coefficient of nitrogen in nickelwere determined from the measured permeabilities of eachalloy and the nitrogen solubilities in nickel.