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 degrees 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.