Research On Behaviors Of Nitriding On Pure Iron By Thermal Plasma Jet Irradiation

Nitriding technology, achieved a great development in the last century, has become a very important technology in surface modification. This technology, however, still has some shortcomings of which the remarkable one is it costs a relative long time to accomplish nitriding process. Many researchers are contributing to find a new method to reduce nitriding time and enhance nitriding efficiency.Thermal plasma, unlike low temperature non-equilibrium plasma, is in the condition of local-thermal-equilibrium (LTE). Ions and almost have same temperature with electrons of which up to 20,000K. The energy of ions is very high, which will benefit accelerating the reaction between N-ions and substrate and increasing nitriding speed.Because of the above reasons, we developed a new device which applied N₂-H₂ thermal plasma jet to nitriding on pure iron. Following results can be drawn:1. Compared with traditional nitriding process, thermal plasma nitriding had a much more increased reaction speed, which proved the feasibility of this technology.2. Temperature had a notable influence on formation of the nitrided layer. The nitrided layer shows different characters under different dispose temperature.3. Surface hardness of the nitrided sample and the N-content in nitrided layer show a certain relationship4. Compared with ion-bombardment nitriding method, different layers of the samples irradiated by thermal plasma can be obtained under a relative high processing temperature. A transform layer was formed between the compound layer and the ferrite iron.