F. Cemin

Physicochemical structure of SiCx:H to improve DLC adhesion on steel

Diamond-like carbon (DLC) coatings show strident properties such as high wear resistance and ultra-low friction. However, a widespread use regarding energy efficiency issues is neglected due to the poor adhesion. Silicon adhesion interlayers (SiCx:H) were deposited at different temperatures from 50 to 500°C with hexamethyldisiloxane followed by DLC. The microstructure was analysed by atomic force microscopy, scanning electron microscopy and Raman spectroscopy. The chemical depth profiling and chemical mapping were performed by glow discharge optical emission spectroscopy and energy-dispersive spectroscopy, respectively. Hardness and critical loads were analysed by nanoindentation tests. At higher deposition temperatures the Si-containing interlayers show lower relative content of H, O and Si and higher relative content of C, allowing the formation of more C–C chemical bonds at the outermost DLC/SiCx:H interface, which is correlated to better adhesion. Finally, an atomistic model is proposed in order to explain the DLC debonding and bonding mechanisms.

Bias influence on titanium interlayer for titanium nitride films

This work investigates the deposition of TiN thin films by cathodic arc evaporation on stainless steel AISI 304 substrate for decorative applications. The applied voltage bias on the substrate during the Ti interlayer deposition was varied, and several properties were determined. The chemical profile, crystalline structure and microstructural properties were analysed by glow discharge optical emission spectroscopy, glancing angle X-ray diffraction and SEM techniques respectively. In addition, nanoindentation and sliding tests were performed in order to evaluate the hardness and scratch resistance of TiN thin films. The results showed that the applied voltage bias during the Ti interlayer deposition step could modify some properties of the TiN thin films. Indeed, lower oxygen contents and higher critical loads to start a plastic deformation (scratch resistance) of the TiN thin films are achieved at higher applied voltage biases during the Ti interlayer deposition. A higher scratch resistance is capable of imparting a long term durability of metallic pieces for decorative applications.

Optical and tribological properties of decorative titanium carbonitride coatings

ABSTRACT Stainless steel and chromium-electroplated metal can change their metallic surface aspects into different colours by thin film deposition technologies. In this study, the colour change of titanium carbonitride (TiCxNy) thin films as a function of N2 and CH4 flow rates in the deposition process was investigated. TiCxNy thin films were deposited by cathodic arc in an industrial equipment at low temperature (125°C) for decorative purposes. The samples were analysed by X-ray diffraction, scanning electron microscopy, glow discharge optical emissions spectroscopy, nanohardness, nanoscratch test and colorimetric analysis. The colour slightly changes from yellow gold to light bronze with carbon addition in the thin film structure. Scratch test determines an increase of the critical load for both plastic deformation and delamination as the carbon content increases. The failure mode shifts from brittle/ductile mode to ductile mode with the increase of the carbon content.