Tribological response and characterization of Mo-W doped DLC coating

DLC coatings and nanostructured carbon coating have been successfully used to prevent against wear and corrosion. Their thermal stability and internal stress have been improved by the addition of transition metals. This work characterizes the surface morphology against two different materials and growth mechanisms of an hydrogen-free carbon coating doped with a W-Mo. The wear resistance is evaluated under dry and room temperature by a set of pin on disc tests at different load and against two different counterfaces, Al2O3 and stainless steel 440 C. The as-deposited and worn surfaces were characterized by electron microscopy techniques, interferometry, nanoindentation and Raman spectroscopy. The as-deposited coating presented a hardness of 14 GPa and an elastic modulus of 179 GPa with a dense surface finished and a columnar structure. The average friction coefficient was between 0.15 and 0.25, with almost no wear on the counterfaces. The W-Mo doped DLC coating showed high resistance against wear with wear rates between 3.79×10−8 mm3 N−1 m−1 and 2.65×10−7 mm3 N−1 m−1 due to its Mo-W carbide content in the amorphous matrix. A major presence of carbides prevent from adhesion to the counterface by reducing the number of dangling bonds.