Sintering iron using an abnormal glow discharge

An abnormal argon-hydrogen glow discharge was used as the basis of an alter native process to sinter metallic materials. In this approach, the sample w orked as the cathode of the discharge and was heated by the bombardment of ions and fast neutral atoms accelerated in the fall voltage of the cathode region. Maintaining the discharge at a low gas flow, a cost-efficient proce ss to sinter materials in a non-oxidizing atmosphere was established. In ad dition, since the samples were heated by the direct bombardment of ions and fast neutrals, plasma sintering may be expected to be an energy-efficient process. As a result, it was observed that the samples were heated above 13 00 degrees C, whereas the temperature of the walls of the reactor did not e xceed 80 degrees C. The process was optimized by setting the total pressure of an 80v/o argon - 20v/o hydrogen gas mixture to 2000Pa (15torr). Porosit y results showed that the plasma enhanced significantly the sintering activ ation of unalloyed iron samples, compared to conventional sintering. Lower porosity was also observed near the surface than in the bulk of the plasma- sintered material. This effect was attributed to sputtering caused by bomba rdment of the sample.