FORMATION OF LOW-FRICTION AND WEAR-RESISTANT CARBON COATINGS ON TOOL STEEL BY 75 KEV, HIGH-DOSE CARBON ION-IMPLANTATION

Hardened AISI D2 steel samples were subjected to mass-separated C+ ion bombardment at 75 keV with ion doses in the range 0.5-15 x 10(18) C+ cm-2. It was observed that sputtering was still limited, and the system exhibited internal growth, because most of the ions penetrated more than 0.1 mum into the growing carbon film. At the lowest ion doses applied, carbon was implanted into the steel, while higher doses resulted in the implanted carbon concentration near the surface being almost 100%. For the highest doses applied, Rutherford backscattering spectrometry and surface profilometry analyses showed that layers about 0.5-1 mum thick of almost pure carbon grew outward from the steel substrate. Transmission electron microscopy showed that the carbon layers were amorphous and exhibited an intermixed layer-substrate interface. The layers were hard and exhibited pronounced elastic recovery when subjected to ultralow load indentation. Low friction and excellent wear properties were measured when tested under dry conditions with a ball-on-disc tribometer.