Influence of Zr and O on the structure and properties of TiC(N) coatings deposited by magnetron sputtering of composite TiC _0.5+ZrO ₂ and (Ti, Zr)C _0.5+ZrO ₂ targets

The effect of Zr and O incorporation on the structure and properties of TiC(N) coatings deposited by DC magnetron sputtering of composite TiC _0.5+xZrO ₂ (x=10 and 20wt.%) and (Ti,Zr)C _0.5+10%ZrO ₂ targets in an argon atmosphere or reactively in a gaseous mixture of Ar+N ₂ is presented. The structure, elemental and phase composition of the coatings were studied by means of X-ray diffraction, scanning electron microscopy, and glow discharge optical emission spectroscopy. The coatings were characterized in terms of their hardness, elastic modulus, and elastic recovery using the load-depth-sensing nanoindentation method. Tribological properties were investigated using ball-on-disk tests against cemented carbide at 25°C and alumina in the temperature range of 25-500°C. To evaluate the oxidation resistance, the coatings were annealed in air at 400, 550, and 600°C for 1h. The obtained results show that the TiZrCO(N) coatings exhibit a peak hardness versus nitrogen partial pressure. The coatings with maximum hardness tested at room temperature against WC+Co and Al ₂O ₃ counterparts showed low friction coefficients below 0.25. At higher temperatures 300-500°C, the friction coefficient against an Al ₂O ₃ ball was recorded to be 0.6. The tribological tests of the coatings demonstrated their high wear resistance at moderate temperatures 25-300°C (wear rate, k~10 ^-6mm ³N ^-1m ^-1). Moreover, the coatings with high Zr content were the most wear resistant. The oxidation resistance of the Zr-doped TiCON coatings was not as high as expected and restricted by 600°C. The combination of high hardness about 40GPa with low friction coefficient and superior wear resistance makes the TiZrCON coatings promising candidates for various dry tribological applications.