Tribological properties of rf PACVD amorphous B-N-C coatings

Amorphous BxNyCz:H films were prepared in a capacitively coupled r.f. PACVD reactor at deposition temperatures <200 degrees C starting from CH4-N-2-B2H6(10% in H-2) gas mixtures. Films were deposited on Si, steel and glass substrates which were placed on the powered electrode. By varying the partial pressure of the gases, the composition was varied in a wide area of the B-N-C triangle. Tribological film properties (wear and friction) were investigated by ball-on-disc testing under humid N-2 (50% RH). B or N additions to pure diamond-like carbon films reduce the wear resistance, while the friction coefficient remains low (0.2) and increases for BN-rich films (>0.5). These results are correlated with the coatings mechanical (depth-sensing indentation) and microstructural (infrared spectroscopy) properties.