2002 Volume 42 Issue 12 Pages 1371-1375
Plasma jets have been successfully used as heat sources of thermal plasma spraying process. However, since the plasma jet is accelerated to supersonic under a low pressure environment, the plasma jets can be used as low temperature plasmas with high chemical reactivity due to supersonic adiabatic expansion and frozen flow. From this viewpoint, nitriding of titanium plates using supersonic expanding nitrogen plasma jets under a low pressure environment was carried out in our previous study. As a result, it was proved that the plasma jets had enough reactivity to form a hard and thick titanium nitride layer on the surface of a titanium plate by only a few minutes of plasma jet irradiation at 30 Pa chamber pressure. In this study in order to develop a practical low temperature and high rate nitriding process, nitriding of nitriding steel, carbon steel and stainless steel using this process was carried out and wear resistance of these nitrided samples was investigated. Consequently, surface hardening was obviously promoted on the condition that hydrogen/ nitrogen mixture gas were used as working gas in the cases of all substrates. Especially, hard layers with over 1000 Hv in hardness were formed without any surface damages on the surfaces of the samples by only 5 min of operation in the cases of nitriding steel and stainless steel. Besides, according to the results of wear testing, wear resistance of these steels was dramatically improved.
