Deposition and mechanical evaluation of superhard Ti–Al–Si–N nanocomposite films by a hybrid coating system

New superhard TiAlSiN films, characterized by a nanocomposite comprising nano-sized (Ti,Al,Si)N crystallites embedded in amorphous Si3N4 matrix, could be successfully synthesized on WCCo substrates by a hybrid coating system of arc ion plating (AIP) and sputtering method. The hardness and Young's modulus value of the TiAlSiN film increased with incorporation of Si, and had the maximum value of ∼55 GPa and ∼650 GPa at the Si content of 9 at.%, respectively. The average friction coefficient of the TiAlSiN films largely decreased with an increase of the Si content. This behavior would be attributed to the tribo-chemical reaction between Si and ambient humidity, which enabled to form SiO2 or Si(OH)2 tribo-layer playing a role as self-lubricant. The harder TiAlSiN film was found to be more wear-resistant against steel. A systematic work on the microstructure and mechanical properties of TiAlSiN films is reported in this paper.