Structure and mechanical properties of Ti-Al-N coatings deposited by combined cathodic arc middle frequency magnetron sputtering

Research highlights: → Ti-Al-N coatings were deposited on Si and WC substrates by combined cathodic arc middle-frequency magnetron (MF) sputtering under a Ti arc power of 10 kW with different Al MF targets currents. The hardness of the Ti-Al-N coatings was in the range of 23-32 GPa, whereas the Young modulus values were in the range of 420-540 GPa. - Abstract: Ti-Al-N coatings were deposited on Si (1 1 1) and WC substrates by combined cathodic arc middle-frequency magnetron (MF) sputtering under a Ti arc power of 10 kW and with different Al MF targets currents. X-ray diffraction patterns (XRD) showed that the Ti-Al-N coatings were polycrystallize with a preferred (1 1 1) orientation at 2θ = 43.7o. The (1 1 1) diffraction showed a decrease in peak intensity but a increase in FWHM values with the increasing of Al contents. Nano-meter sized TiN crystal grains distinguished by the lattice fringe contrast were verified by plan-view transmission electron (TEM) and selected area electron diffraction (SAED) images. With the increasing of MF sputter currents from 5 to 20 A, the Al contents in the Ti-Al-N coatings monotonically increased from 4.8 to 10.8 at.%, whereas the N and O contents were nearly constant. The hardness of the Ti-Al-N coatings was in the range of 23-32 GPa, and the Young modulus values were in the range of 420-540 GPa.