Effects of N2 partial pressure on microstructure and mechanical properties of cathodic arc deposited TiBN/TiAlSiN nano-multilayered coatings

Nanocomposite coatings have become promising protective materials due to their high hardness and anti-wear properties applicable in high-speed dry cutting and grinding tool industries. The monolithic TiN, TiBN, TiAlSiN and hierarchical TiBN/TiAlSiN coatings were deposited on Si and cemented carbide substrates at various N2 partial pressures using a cathodic multi-arc ion plating system wherein the alloyed TiB2 and TiAlSi targets were selected as cathodes. The microstructure, composition and morphology were measured by XRD, XPS, SEM, HRTEM and AFM, respectively. Nanoindentation and ball-on-disc friction testing were performed to investigate the mechanical and tribological properties of the coatings. The results show that TiBN/TiAlSiN coatings compose of numbers of alternating TiBN and TiAlSiN sublayers with a few nanometer periods. As compared to hardness beneath 28 GPa and coefficient of friction over 0.50 for monolithic TiBN and TiAlSiN coatings fabricated at 2.0 Pa, the TiBN/TiAlSiN multilayered coatings possess a microhardness value of 34 GPa with the lowest COF of 0.29, while the maximum value can reach 38 GPa on samples prepared at 1.0 Pa. Their mechanical and tribo-logical properties are superior significantly to the monolithic TiBN or TiAlSiN, which pave the way for fabricating hard/lubricant nanosized multilayered coatings for application on dry-cutting and grinding tools.