Effect of Bias Voltage Deposition and Hydrogen Etching on a-SiC _<i>x</i> :H Interlayer to Tailor a-C:H Film Adhesion on the Ti6Al4V Substrate

Hydrogenated amorphous carbon (a-C:H) is a low-friction, high hardness, and chemically inert material belonging to the diamond-like carbon group. This film can cover the poor tribological properties of Ti6Al4V, potentially extending the application of this alloy to the tribological area. However, the adhesion of this film on many metallic substrates, such as Ti6Al4V, is low due to its thermal expansion mismatch and high residual stress. To mitigate these phenomena, an intermediary film, known as an interlayer, can be applied. In this study, the plasma-enhanced chemical vapor deposition technique was used to plasma etch Ti6Al4V substrates, deposit hydrogenated amorphous silicon carbide (a-SiCx:H) interlayers from tetramethylsilane, and deposit a-C:H films. Different bias voltages were applied in the interlayer deposition, and different H2 relative flows were used to feed the etching stage. Optical emission spectroscopy was used as a plasma diagnostic tool. The films were analyzed with physicochemical and microstructural characterizations, and their adhesion was evaluated through scratch tests. It was found that the interlayer thickness reached its maximum by using 600 V. Higher bias voltages produced interlayers with a higher carbon content and lower silicon content. The films’ adhesion to the substrate was not affected by changes in bias voltage applied in the interlayer deposition. Increasing the H2 relative flow up to 40% in the etching stage enhanced the films’ adhesion, while the delamination occurred at the a-SiCx:H/Ti6Al4V interface.