Influence of process atmosphere circulation on the distribution of nitriding conditions in unconventional active screen plasma nitriding (ASPN) systems

The aim of this work is to verify the possibility of designing an active screen plasma nitriding (ASPN) process with a controlled gas flow direction in order to implement multifunctional hybrid devices. The specimens have been subjected to nitriding processes under the established process conditions in which two different gas flow directions have been used. In the first configuration, the gas has been supplied at the top part of the chamber and pumped out from the bottom part of the chamber. In the second configuration, the gas has been supplied at the bottom part of the chamber and evacuated from its top part. The distribution of hardness and thick-ness of the nitrided layers has been evaluated on the prepared metallographic cross-sections. The results of material tests have been compared with the results of simulation tests showing the circulation of the atmosphere inside the process chamber. The presented research results show that using both gas flow directions and the unconventional shape of the process chamber it is possible to carry out efficient nitriding processes. However, further research is necessary to obtain a homogenous layer in the entire chamber space.