Study on formation of functional Cr ceramics film by disproportionation reaction

采用氯化物熔盐浸渍法在氮化钢表面制备氮化铬陶瓷膜。成膜反应是基于铬离子在熔盐中的还原反应。膜层由氮化铬、CrN和Cr_2N以及Fe-Cr固溶体组成，膜层厚度与处理温度、时间和镀液成分有关。薄膜的硬度在1300 ~ 3000 Hv之间。由于铬的表面扩散防腐层，使其在常温氯化物水溶液中具有良好的耐蚀性。采用两步法可在钢表面形成CrSi_2复合膜。因此，可以在不含成膜元素的试样上，采用熔盐分步处理的方法制备陶瓷膜。

Chromium nitride ceramics film was formed on the nitrided steels by immersing in chloride molten salts with chromium fluoride and ferro-chromium. Film formation reaction is based on the disproportionation reaction of chromium ions inmolten salts. The film consisited of chromium nitride, CrN and Cr_2N, and Fe-Cr solid solution, of which thickness depended on the treatment temperature, time and bath composition. The film showed high hardness from 1300 Hv to 3000 Hv. It has a good corrosion resistance in aqueous chloride solution in ambient temperature due to the surface diffusion anti-corrosive layr of chromium. Moreober, complex Cr-Si film, CrSi_2, could be formed on the steel by two step techniques. Therefore, It can be possible to make ceramics films on the specimen, which has no element for films, by using a multistep treatment in the molten salt.