鐵鋁基二元合金在含H2/NH3/Ar混合氣氛下之氮化行為研究

The Nitridation Behavior of Fe-Al Binary Alloys in H2/NH3/Ar Mixed Gases

本文探討純Fe及Fe-Al合金於H2/NH3/Ar氣氛下，溫度500～700℃間的氮化行為。研究顯示純Fe及Fe-20Al、Fe-28Al及Fe-40Al合金在各個溫度之氮化動力學皆遵守拋物線行定律，且氮化反應速率隨鋁含量之增加，呈現不同程度之減慢，而純鐵的氮化反應速率在600℃～700 ℃間有動力學逆轉發生。經由XRD分析合金氮化後得知，表層都皆以Fe3N和Fe4N之混合氮化物存在，而內層則有AlN之形成，其中AlN的生成是造成Fe-Al基二元合金氮化較純Fe慢的主因。

The purpose of the research is to study the nitridation behavior of pure iron and three Fe-Al alloys (containing Fe-20Al, Fe-28Al, and Fe-40Al at.%) over the temperature range 500 ~700℃ in a H2/NH3/Ar gas mixture. The nitridation kinetics followed the parabolic rate law, and the nitridation rates generally decreased with increasing Al content. The kinetics inversion was observed 600℃～700℃ for pure Fe. The nitrides formed on pure Fe consisted of mostly Fe4N and minor Fe3N, while the nitrides formed on Fe-Al alloys consisted of mostly Fe4N, Fe3N, and minor AlN. The amount of AlN gradually increased form the surface to the interior scales. It is believed that the formation of AlN is responsible for the reduction of nitridation rates of Fe-Al alloys, as compared to those of pure Fe.