STRUCTURE AND WEAR PROPERTIES OF CARBON IMPLANTED 304-STAINLESS STEEL USING PLASMA SOURCE ION-IMPLANTATION

Methane plasma source ion implantation was used to implant carbon ions into 304 stainless steel. This paper examines the effects of high voltage pulse repetition rate on the structure and wear properties of implanted samples. The implantations were carried out at a target bias of -30 keV to a dose of 3 x 10(17) atoms cm-2. Three repetition rates (42 Hz, 87 Hz and 126 Hz) were used. At low repetition rate, a carbon coated-implanted surface forms, while only an implanted surface is produced at high repetition rates. Metastable phases were observed and identified, and the microstructure at the surface was observed to be dependent on the chosen implantation parameters. Fe2C formed in the implantation layer which is produced at 42 Hz. Smaller size Fe2C and other forms of carbides (possibly Fe3C and/or (Cr, Fe)7C3) formed in samples implanted at 87 Hz. An increase in repetition rate to 126 Hz produced a shallower amorphous implantation layer. Possible explanations of phase formation mechanisms are given. Wear resistance of all the implanted samples was improved, with the coated-implanted sample produced at 42 Hz showing the greatest improvement. The mechanism of wear was observed to change from an adhesive mode to a mild abrasive mode after implantation.