Nanometric chromium/chromium carbide multilayers for tribological applications

Metal/ceramic multilayers with periods in the nanometric range have been proposed as protective coatings due to their improved tribological and mechanical properties as compared to single coatings. We have evaluated nanometric chromium/chromium carbide (Cr/CrC) multilayers as a promising combination for tribological applications. These multilayers were synthesized by r.f. magnetron sputtering from a pure chromium target onto steel and silicon substrates. The multilayer structure was obtained by alternatively changing the sputtering gas composition between pure argon and a reactive mixture Ar/CH4. The total coating thickness was approximately 1.5 μm, and the bilayer period varied from 300 to 20 nm. Secondary ion mass spectrometry and scanning electron microscopy confirmed the periodic multilayered structure. X-ray diffraction allowed us the characterization of the different crystallographic phases formed in the Cr/CrC system. The influence of deposition parameters and period thickness on the coatings microstructure and mechanical properties is presented in this work.