Oil removal and nitriding of sintered parts using a DC discharge

Results of oil removal and nitriding of sintered parts are presented. Plasma technology was used for the sample cleaning as well as for nitriding. The whole process was carried out in the same reactor and in a single thermal cycle. Metallic pieces of unalloyed iron were produced by compaction at 600 MPa and sintered in a conventional resistive furnace at 1150 °C. Samples were stored in oil for 30 days and treated in argon and hydrogen plasma. The electric discharge was generated in a confined electrodes configuration, with the samples placed on the anode. The sample cleaning was characterized by mass loss measurements, and the results have shown that a hydrogen discharge was more efficient than an argon one. Maintaining the temperature at 300 °C, the majority of oil was removed for a time processing of 10 min. After the plasma cleaning of the samples stored in oil, surface treatment was carried out in nitrogen/hydrogen gas mixture with the sample working as the cathode and anode of the confined discharge. Similar nitrided layers were obtained for samples stored and not stored in oil, as well as for treatment performed in the cathode or anode configuration.