Low Friction-Coefficient TiBCN Nanocomposite Coatings Prepared by Cathode Arc Plasma Deposition

TiBCN nanocomposite coatings were deposited on cemented carbide and Si (100) by a cathode arc plasma system, in which TiB ₂ cathodes were used in mixture gases of N ₂ and C ₂ H ₂ . X-ray diffraction shows that TiB ₂ and Ti ₂ B 5 peaks enhance at low flow rates of C ₂ H ₂, but they shrink when the flow rate is over 200 sccm. An increase of deposition rate was obtained from different TiBCN thicknesses for the same deposition time measured by scanning electron mi- croscopy. Atomic force microscopy shows that the surface roughnesses are ∼10 nm and ∼20 nm at C ₂ H ₂ flow rates of 0-100 sccm and of 150-300 sccm, respectively. High resolution transmis- sion electron microscopy and X-ray photoelectron spectroscopy show that the coatings consist of nanocrystal phases Ti ₂ B ₅, TiB ₂ and TiN, and amorphous phase carbon and BN. The average crystal sizes embedded in the amorphous matrices are 200 nm and 10 nm at C ₂ H ₂ flow rates of 200 sccm and 300 sccm, respectively. In Raman spectra, the D- and G-bands increase with C ₂ H ₂ flows at low flow rates, but weaken at high flow rates. The microhardness of the coatings decreases from 28.6 GPa to 20 GPa as the C ₂ H ₂ increases from 0 sccm to 300 sccm, and the ball-on-disk measurement shows a dramatic decrease of the friction coefficient from 0.84 to 0.13. The reason for the reduced hardness and friction coefficient with the change of C ₂ H ₂ flow rates is discussed.