Influence of the negative bias in ion plating on the microstructural and tribological performances of Ti-Si-N coatings in seawater

The TiSiN coatings were deposited on Ti6Al4V alloy by multi-arc ion plating with different substrate negative bias to improve the tribological properties of titanium alloy in seawater. The TiSiN coatings have a coupled structure of amorphous Si3N4 and nanocrystalline TiN. The grain size decreases and the coatings become dense with the increase of the negative bias. The hardness of TiSiN coatings increases from 39 GPa to 47 GPa with the increase of substrate negative bias from 10 V to 40 V. The tribological tests reveal that the TiSiN coatings have a lower friction coefficient and higher wear rate in seawater compared with in atmosphere. Moreover, the wear rates increase with the increase of bias voltage. The TiSiN coating deposited at bias voltage of 10 V shows the best tribological properties in seawater.