Abstract
Carbon ions were implanted into hardened high-speed tool steel by means of a plasma immersion ion implantation (PIII) technique with methane gas. Various process times were used in order to investigate the relationship between mechanical properties and depth distribution of carbon, and to examine whether it is possible to apply PIII for practical use for commercialized high-speed tool steel substrate. The implanted surface was characterized by X-ray diffractmeter (XRD) for investigation of surface structure. Auger electron spectroscopy (AES) was used to determine the depth distribution profile of the elements in substrate. Raman spectroscopy was also utilized for the characterization of carbon film deposited on the substrate. Substrate temperature was estimated from the hardness of a tool steel substrate treated simultaneously. Substrate temperature did not exceed the tempering temperature of high-speed tool steel, and was below 532K. Short term implantation with −20kV of negative bias caused a high concentration of carbon at the steel surface. On the other hand, carbon film was deposited on the carbon enriched surface by long term implantation. Raman spectrum for the deposited carbon film showed that for a typical DLC film. Friction test with a bearing steel ball as a counter material was similar to that the friction coefficient of deposited DLC film, carbon implanted layer, and steel substrate were 0.2, 0.3 and over 0.5, respectively. These results suggest that PIII with methane is feasible for the surface treatment of high-speed tool steel as both the implanted carbon and the DLC film reduce its friction coefficient in dry conditions.
