Application of Quasi-Direct-Current Plasma Immersion Technique to Enhancement of Surface Properties of Automobile Components

South China is one the major automotive component producing centers in the world and the Hong Kong government has specified automobile parts as a major industrial direction. In this project, we propose to investigate the application of the quasi-direct-current plasma immersion technique to enhance the surface properties of piston rings used in automotive engines. This novel technique which is developed and patented by the Plasma Laboratory of City University of Hong Kong offers better treatment uniformity for three-dimensional samples. We propose to improve the tribological properties of piston rings by optimizing surface nitridation conducted by means of quasi-direct-current nitrogen plasma immersion ion implantation (DC-PIII) at elevated temperature. Unlike conventional plasma immersion, DC-PIII allows the use of a high pulsing frequency as well as high bias voltage to increase the incident ion flux without the risk of plasma extinction. A high ion current heats the piston rings quickly and accelerates nitrogen diffusion into the alloys enabling the formation of a thick nitrided layer required by the automotive industry.