TRIBOLOGICAL AND STRUCTURAL-PROPERTIES OF 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% diluted in H-2) gas mixtures. The composition (B,N,C ,H) was analysed with electron probe microanalysis and elastic recoil detection. Tribological film properties (wear and friction) were inves tigated by ball-on-disc testing under dry and humid N, atmospheres. Ha rdness and Young's modulus were determined by depth-sensing indentatio n measurements. It will be shown that among the wide range of composit ions investigated, the pure amorphous carbon films (a-C:H) remain unsu rpassed with respect to wear and friction behaviour. The addition of B and/or N to a-C:H films reduces their hardness and wear resistance, w hile the friction coefficient remains low (0.2) and increases for BN-r ich films (> 0.5). As an exception, a striking similarity is found bet ween a-B:H and a-C:H films with respect to their mechanical properties (hardness, Young's modulus). Nevertheless, these a-B:H films also sho w a much lower wear resistance in a ball-on-disc test due to different friction mechanisms related to the formation of transfer layers. Thes e results are correlated with the microstructural properties of the co atings as determined from infrared spectroscopy and Raman spectroscopy .