Sputter Deposited Nanocomposite Cr-Based Films and Their Characterization

Abstract

The Cr-C-N films with varied N concentrations (45.3–25.5 at.%), controlled by closed loop optical emission monitoring, were deposited onto Si(100) and M42 steel substrates by reactive magnetron sputtering technique. The deposited films were characterized by employing X-ray photoelectron spectroscopy (XPS) for elemental composition and bonding state, X-ray diffraction (XRD) for crystal structure, Pin-on-disc (POD) test for friction coefficient, Rockwell-C test and Scratch tests for adhesion and Nanohardness test. It is found that variation in N concentration influences the structure and thus the properties. The phase structure changes from CrN + Cr for samples with N/Cr = 1.16–0.95 (at.%) to β-Cr2N + CrN + Cr for samples with N/Cr = 0.80–0.42. Film with N/Cr = 0.80, possesses the highest nanohardness of 27.3 GPa comprising of Cr2N + CrN + Cr phases. The lowest achieved friction coefficient value was 0.36 and lowest specific wear rate of 2.1 × 10−8 mm3/Nm, in the pin-on-disk wear test which was mainly due to the combination of the two factors: growth of hard Cr2N phase and high carbon content of 20.6 at.% in the film. The low friction coefficient and wear values are due to the presence of high carbon content. The scratch test provided best adhesive and cohesive properties with critical load as high as LC2 = 72.9 N for the hardest film. Rockwell-C adhesion tests demonstrated adhesion strength HF2 for the hardest film.