Plasma nitriding potential and a new modeling approach for plasma nitriding process control

Plasmanitriding is a thermochemical surface heat treatment processes of steel components to produce nitride layers which increase wear-, corrosion- and fatigue resistance. Research on plasmanitriding lately showed that there is a significant and characteristic amount of ammonia formed off the process gases nitrogen and hydrogen. Aim of the research work is to analyze the influence of plasma treatment parameters, such as pressure, voltage, temperature, and nitrogen to hydrogen ratio on the atmosphere and the formation of ammonia during plasmanitriding. The ammonia-content is measured in the exhaust gas. By correlating the measured ammonia with the treatment parameters and modeling the nitriding process, the ammonia-content can be predicted. Further, a plasma nitriding potential is calculated, comparable to the gas nitriding potential based on the ammonia-content, and its practicability as process control parameter is shown by correlating the potential with the nitriding results, e.g. the formation of ε and γ' nitride phases.