Influence of increased voltage on the nitriding zone during plasma nitriding

Abstract

AbstractPlasma nitriding is an established process for increasing the corrosion and wear resistance of steel. However, the possibilities of modern developments in the field of high‐voltage plasma power supplies have been hardly investigated. For example, modern plasma generators allow improved arc management, which enable plasma nitriding at higher voltages.In the present work, the influence of increased voltage (up to 800 V) on the nitriding of a ferritic steel X38CrMoV5‐1 was investigated. It was found that the thickness of the compound layer increases with increasing voltage. Especially at short process times the increased voltage leads to increased growth. An increase in the nitriding depth was also observed.Furthermore, the increased voltage has an effect on the composition of the compound layer too. A moderate increase in ϵ‐nitride in the compound layer was observed.One explanation for the observed behavior is the over proportional increase in power with increasing voltage, indicating an increased ionization rate of the plasma. Due to this, more diffusible species would be available for nitriding.The presented results could be used to reduce process times, particularly where the formation of a compound layer is the aim of the process. An example of such a process is oxy‐nitriding.