Volume 3, Issue 3 (March 2006)
Plasma Assisted Heat Treating Processes of Bearing Components
Plasma surface-engineering technologies show several advantages over conventional surface engineering. In this paper the basic properties of a glow discharge plasma process and the way it is used for industrial applications is demonstrated via plasma nitriding and plasma carburizing of bearing parts. Plasma nitriding was applied for duplex hardening (DH) of bearing parts made from M50 and M50 NiL material. The influence of the process parameters on hardness profile and microstructure of the diffusion layer formed during nitriding is shown. By metallurgical evaluation of many specimens, located at different positions in the furnace, the uniformity of the process is demonstrated. Results of several rig tests show the superiority of the nitrided bearings but also confirm the importance of close control of the nitriding process. Plasma carburizing processes were applied on bearing parts made from M50 NiL material. The mechanical and thermo chemical pre-treatment of the surface can be replaced by an initial sputtering which improves the reliability of the process. Hardness profiles, microstructure, and residual stress profiles of the carburized zone are comparable to those from gas carburizing.