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_2H_2.X-ray diffraction shows that TiB_2 and Ti_2B_5 peaks enhance at low flow rates of C_2H_2,but they shrink when the flow rate is over 200 seem.An increase of deposition rate was obtained from different TiBCN thicknesses for the same deposition time measured by scanning electron microscopy.Atomic force microscopy shows that the surface roughnesses are ~10 nm and ~20 nm at C_2H_2 flow rates of 0-100 sccm and of 150-300 sccm,respectively.High resolution transmission electron microscopy and X-ray photoelectron spectroscopy show that the coatings consist of nanocrystal phases Ti_2B_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_2H_2 flow rates of200 sccm and 300 sccm,respectively.In Raman spectra,the D- and G-bands increase with C_2H_2flows 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_2H_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_2H_2 flow rates is discussed.