Deposition and characterization of a ZrN/Zr/a-C multilayer: Implication on bio-tribological and corrosion behaviors

- ZrN/Zr/a-C multilayer is deposited by magnetron sputtering.
- The structure of ZrN is fcc while that of Zr is hcp.
- ZrN/Zr/a-C multilayer shows a high hardness of 18.7 GPa and low residual stress.
- ZrN/Zr/a-C multilayer exhibit excellent bio-tribological behavior.
- The corrosion resistance is improved by ZrN/Zr/a-C multilayer.

The ZrN/Zr/a-C multilayered coatings were deposited onto Ti6Al4V and Si substrates using a closed field unbalanced magnetron sputtering. The morphology and microstructure of the multilayers were performed by scanning electron microscopy (SEM), atomic force microscopy (AFM) and transmission electron microscopy (TEM). The multilayer consists of a-C layers, Zr layers and ZrN layers. The Zr interlayers can improve the weak adhesion between a-C layers and ZrN layers. The multilayer exhibits a low residual stress of − 0.5 GPa and a hardness of 18.7 GPa. The tribological properties were evaluated by a ball-on-disk tribometer. The friction coefficient and wear rate of the multilayer in fetal bovine serum (FBS) kept very low values during sliding at an applied load of 2 N, which indicated excellent long-term wear resistance. What is more, the multilayer also presented a low wear rate in FBS even at a high applied load of 10 N. Additionally, the corrosion resistance of Ti6Al4V in Hank's solution is significantly improved by the multilayer. This study demonstrates that the ZrN/Zr/a-C multilayer exhibits excellent performance including low residual stress, high corrosion resistance as well as good bio-tribological properties and it is proper to protect Ti6Al4V alloy.