Multifunctional Wear and Corrosion Resistant Decorative Nanostructured Carbon-Base Coatings

Multifunctional wear and corrosion resistant decorative nanostructured carbon-base coatings were prepared by PACVD (Plasma Assisted Chemical Vapour Deposition) method on steel substrates. As the multifunctional coating the carbon-base, particularly DLC (Diamond-Like Carbon) nanolayer, was chosen. For the deposition of adherent DLC coating on steel substrate a very thin Si-O-C interlayer was applied in some cases. Deposition of DLC coating and Si-O-C interlayer was performed using dc plasma without additional heating and with the HMDSO (hexamethyldisiloxane) and methane as precursors. During coating growth with increasing of thickness of DLC nanolayer the colour of nanolayer is changed. Whole spectrum of attractive colours is obtained, what is possible to use to decorative purposes. Effect of film thickness on colour is following: The reference specimen (bare stainless steel) has a bright metallic sheen. In the order of increasing thickness, the DLC films produced by PACVD have colours as follows: dark violet at ~75 nm; medium blue at ~130 nm; golden light at ~170 nm; deep rose pink at ~240 nm; golden brown at ~320 nm; and soot black at ~1200 nm. Decorative coatings must be adherent and hard for good wear resistance. Adhesion was tested by scratchtester and microhardness was determined by nanoindentation. The microhardness data were thickness-dependent, influenced by substrate. The highest measured value was 23 GPa. Tribology of the coatings was assessed by wet friction tests.