Practical and Economical Effects of the Use of Screen Meshes for Steel Nitriding Processes with Glow Plasma

Abstract

The dynamically developing energy sector forces technologists to create new materials that meet the increasingly higher mechanical, chemical, and electrical requirements. The paper relates to the method of reducing the energy consumption of the plasma nitriding process of austenitic steels. The method proposed by the authors involves the modification of nitriding technology in glow plasma. It consists of introducing perforated screens between the anode and nitrided surface made of a material with a composition similar to the processed material and the use of an HF power supply with controlled mean current generating negative voltage peaks of about 1000 V. Nitriding is carried out in a nitrogen-hydrogen atmosphere. The processed material has a negative potential in relation to the surrounding plasma and strongly negative in relation to the vacuum chamber jacket. The actual treatment is preceded by ionic cleaning of the surface of the detail and heating it to the temperature that activates the diffusion processes. The authors analyse the dynamic distribution of electric fields generated at the surface of the nitrided material with different configurations of the cathode-sample-screen system, trying to find the correlation of treatment parameters with the parameters of the nitrided layer. A significant influence of the screening meshes on the depth of the obtained diffusion layers containing nitrogen was found. The oscilloscopic measurements of the plasma in the boundary layer allowed for the observation of voltage peaks, probably leading to an increase in the peak kinetic energy of nitrogen ions and their easier penetration into the material. The work is of a cognitive nature and is probably one of the first to look for relationships between the dynamic electrical parameters of plasma and the efficiency of nitriding.