Friction and wear properties of CrN coatings sliding against Si3N4 balls in water and air

CrN coatings were deposited on 2024Al alloy using arc ion plating apparatus. The CrN coatings’ topography was observed by using scanning electron microscopy (SEM). The composition and structure of CrN coatings were determined by energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The reciprocating sliding friction and wear characteristics of CrN coatings against Si3N4 ceramic balls in water and air were investigated by using the ball-on-disk configuration with 1 mm amplitude (A). The influences of normal load (W) and reciprocating frequency (f) on the friction coefficients (μ) and the specific wear rate of CrN coatings were studied. The worn surfaces on CrN coatings were observed by SEM and analyzed by EDS. The results showed that there were many white particles and dimples on gray surface. The Cr and N concentrations for the white particles were higher than those of gray parts. With increases in the normal load and reciprocating frequency, the friction coefficient all decreased in air and water, while the CrN coatings’ specific wear rate decreased with normal load, and slightly fluctuated with reciprocating frequency. The friction coefficient decreased linearly with frictional energy (μWfA), and the logarithmic values for the CrN coatings’ specific wear rate increased linearly with friction coefficient (μ), while decreased linearly with frictional energy (μWfA). The microanalysis of the worn surface of CrN coatings indicated that the formation of tribofilms with the Cr–N–Si–Al–O was occurred during friction testing.