WEAR-RESISTANT STEEL SURFACES OBTAINED BY HIGH-DOSE IMPLANTATION OF CARBON

Carbon ions were implanted into hardened and unhardened Sverker 21 and Thyrapid 3243 steels with doses ranging between 0.5 x 10(18) and 2.0 x 10(18) C+ cm-2 and with ion energies of 75 and 150 keV. Friction and wear were measured with pin-on-disk tribometers, both unidirectional and reciprocating. The coefficient of friction was moderatley reduced, from about 0.8 to 0.2-0.5, by the surface modification induced. In several cases a dramatic decrease in wear was observed. The wear behaviour was very dependent on the tribological test conditions (unidirectional or reciprocating test, relative humidity and test atmosphere (air, O2 or N2)). Stoichiometry and structural properties were investigated with Auger analysis, transmission electron microscopy and selected-area electron diffraction. The ion-carbonized surfaces were amorphous, and peak carbon concentrations of up to around 90 at.% were measured. The main part of the implanted carbon was present as graphite or amorphous carbon.