A study of a proposed plasma nitriding system, exploiting the hollow cathode effect, with treated part biased to anodic potential (Anodic Plasma Nitriding in Hollow Cathode – HCAPN) is presented. The aim of the study was to investigate the differences and similarities with conventional Active Screen Plasma Nitriding (ASPN). At the same time, the experimental results i. e. optical and scanning electron microscopy study of white and diffusion layer along with micro-hardness measurements are presented. Furthermore, the ammonia formation during the nitriding process was studied at different temperatures. We showed that the amount of ammonia reaches a maximum value at 700 K and at higher temperatures the amount of ammonia gradually decreases. This indicates that at the higher temperatures more and more of the formed ammonia dissociates (decomposes) on the hot surfaces of the sample and cathode, transferring the nitrogen to these surfaces, as in the case of classic gas nitriding.

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The paper deals with the design of a new plasma diagnostic system consisting of a microcontroller based power supply for automatic control of the measurement using Langmuir probe, the communication interface of the power supply and the signal processing program. The main motivation for the design of the automated plasma diagnostic system was given by our research in different methods of plasma nitriding of steels. During the nitriding process, it is important to achieve information about the plasma, which is the medium where the heat-treatment process is going on. The new diagnostic system is able to perform measurements during the nitriding process, thus we can analyze the plasma at different temperatures and gas mixtures. The obtained voltage-current curves are recorded and transmitted to the computer, where further signal processing is performed. The paper presents the design of the power supply, the measurement results and the developed signal processing software.