Microstructural, mechanical and tribological analysis of nanocomposite Ti-C-N coatings deposited by industrial-scale DC magnetron sputtering

Nanocomposite coatings consisting of Ti(C,N) nanocrystallites embedded in an amorphous carbon-based matrix were studied. The coatings were deposited by reactive DC magnetron sputtering in an industrial-scale deposition system. The microstructure and mechanical properties of the films were studied as a function of the N2-fraction in the sputter gas and the deposition temperature. It was suggested that the chemical compositions and deposition rates were governed by a complex interplay between target poisoning and chemical sputtering of the growing film. From the chemical compositions, the content of amorphous matrix was estimated to be up to 57%. It was found that the highest amount of crystalline material was obtained at low N2-fractions in the sputter gas, which coincided with the highest concentration of titanium in the coatings. An overall dependence of the hardness and the elastic modulus on the estimated content of amorphous phase was found for amorphous phase contents exceeding about 20%. It was suggested that the mechanical properties were mainly controlled by the amorphous matrix. A pin-on-disc test revealed that a higher N2-fraction in the sputter gas resulted in a higher wear rate, whereas similar friction coefficients were obtained independent on the N2-fraction.