Microstructure and mechanical properties of quaternary Cr–Si–O–N films by a hybrid coating system

Quaternary Cr–Si–O–N films were deposited by a hybrid coating system using a Cr cathodic arc target and a Si sputtering target in an Ar/N2/O2 gaseous mixture. The influence of oxygen flux rate on the microstructure and properties of the Cr–Si–O–N films were investigated. The results indicated that the oxygen-free Cr–Si–N film exhibited nanocolumnar microstructure containing CrN nano columns and amorphous Si3N4 phase. The Cr–Si–O–N films exhibit equiaxed CrN nanocrystallites likely surrounded by amorphous SiO2 and Si3N4 phases. Further increasing the oxygen content gives films containing Cr2O3 crystallites. The hardness first increases from 30 GPa for the Cr–Si–N film to a maximum value of approximately 50 GPa for the oxygen content of 16 at.% and then decreases for larger oxygen content. All the Cr–Si–O–N films exhibit low friction coefficient (0.22–0.26) and low residual stress (− 0.03–0.08 GPa). The influence of the oxygen content on the microstructure and mechanical properties of the Cr–Si–O–N films is discussed.