Mechanical properties of Cr-O-N coatings deposited by cathodic arc evaporation

Ternary chromium based coatings (Cr-O-N) were formed on HS6-5-2 steel substrates using a vacuum arc plasma flux coating system at different relative oxygen concentrations, O-2(x) = O-2/(N-2 + O-2). The mechanical and tribological properties of the coatings were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), hardness measurements, wear test and adhesion tests (scratch test and Daimler-Benz test). Special attention was paid to coating adhesion and failure modes in the adhesion tests. The coefficient of friction, wear rate and adhesion decreased as the relative oxygen concentration increased. Hardness of the coatings showed the opposite effect, increasing from approximately 19 GPa-30 GPa. The dominant failure mode of Cr-O-N coatings was abrasion. Individual micro fragmentation was also observed for Cr-O-N coating with O-2(x) = 20%.