High Temperature Nitridation Behavior of Fe-Al Base Alloys in H2/NH3/Ar Mixed GAses
| Autor: | H. Y. Tsai, 蔡和遠 |
|---|---|
| Rok vydání: | 2002 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 90 The nitridation of behavior of Fe-Al based binary or ternary alloys (containing Fe-2, 10, 20, 28, 40 Al and Fe-28Al-2M where M=Mo, Cr, Nb or Y and Fe-28Al-10Mo, all in at.%) was studied over the temperature range 500∼700℃ in a H2/NH3/Ar gas mixture. The nitridation kinetics of Fe-Al based binary and ternary alloys followed the parabolic rate law, and the nitridation rates of Fe-Al binary alloys generally decreased with increasing Al content, and the kinetics inversion was observed between 600℃and 700℃ for pure Fe. The nitridation rates of Fe-28Al were significantly reduced by adding 2 at.% of Nb or 10 at.% Mo, but only slightly reduced by adding 2 at.% of Cr or Y. On the other hand, the nitridation rates of Fe-28Al were slightly increased by adding 2 at.% Mo. The nitrides formed on the surface of Fe-Al binary alloys consisted of mostly Fe4N and Fe3N, while amount of minor AlN was observed in the inner scale layer. It is believed that the formation of AlN is responsible for the reduction of nitridation rates of Fe-Al binary alloys, as compared to those of pure Fe. The nitrides formed on Fe-Al tenary alloys were strongly dependent on alloying elements, being similar to Fe-28Al for alloys contain 2 at.% Mo, Cr, and Y. However, slight amounts of NbN and MoN were detected on Fe-28Al-2Nb and Fe-28Al-10Mo, respectively, whose formation is responsible for the reduction of nitridation rates of Fe-28Al base ternary alloys. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
| Externí odkaz: |
|