Wear resistant multilayer nanocomposite WC1−x/C coating on Ti–6Al–4V titanium alloy

• Proposed multilayer coating system can reduce the wear volume on Ti–6Al–4V up to 94%.
• System consist of diffusion hardening (O2, N2), TiCxNy gradient layer, WC1−x/C layer.
• Hardness of the TiCxNy layer change gradually improving adhesion of WC1−x/C layer.
• Coefficient of friction decrease only 10% comparing to uncoated Ti–6Al–4V.

A significant improvement of tribological properties on Ti–6Al–4V has been achieved by developed in this study multilayer treatment method for the titanium alloys. This treatment consists of an intermediate 2 μm thick TiCxNy layer which has been deposited by the reactive arc evaporation onto a diffusion hardened material with interstitial O or N atoms by glow discharge plasma in the atmosphere of Ar+O2 or Ar+N2. Subsequently, an external 0.3 μm thin nanocomposite carbon-based WC1−x/C coating has been deposited by a reactive magnetron sputtering of graphite and tungsten targets. The morphology, microstructure, chemical and phase compositions of the substrate material after treatment and coating deposition have been investigated with use of AFM, SEM, EDX, XRD, 3D profilometry and followed by tribological investigation of wear and friction analysis. An increase of hardness in the diffusion treated near-surface zone of the Ti–6Al–4V substrate has been achieved. In addition, a good adhesion between the intermediate gradient TiCxNy coating and the Ti–6Al–4V substrate as well as with the external nanocomposite coating has been obtained. Significant increase in wear resistance of up to 94% when compared to uncoated Ti–6Al–4V was reported. The proposed multilayer system deposited on the Ti–6Al–4V substrate is a promising method to significantly increase wear resistance of titanium alloys.

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