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.
The efficiency and morphology of boron deposition have been investigated in a glow discharge, using a BCl3-H2 mixture. The efficiency of reaction depends on the initial BCl3 concentration and the gas flowrate. The maximum efficiency was 27% at 800° C using an initial BCl3 concentration of between 0.2 and 10 vol. -%. Under these conditions the boron condensed on the caihode as slightly overlapping spiral crystals. The quantity of condensed boron increases linearly with higher initial BCl3 concentration, and thus the reaction should be considered as being first order relative to the BCl3 concentration.
Knowledge of the surface emissivity of metals is becoming more and more important both from the material science, process modelling and control point of view. Previous research results have shown that the emissivity of most metals depends on the temperature of the surface. It has also been reported that the most important temperature region is between 300 – 1000 K degrees, where the change of the emissivity is the most intense, which is also the most significant from a process control point of view [1]. We also report temperature dependent emissivity observed during plasma nitriding of low alloy steels [2]. Related to one of our present research topics the study of the low alloy aluminum (AlMg1, AlMg3) emissivity has prooven relevant. In this article the developed emissivity estimation model is presented. In the first part a literature overview and the theoretical approach of the new method is discussed, followed by the experimental results for low alloy aluminium emissivity determination and a comparison with the results available in the literature.
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