Nanotribological properties of wear resistant a-CNx thin films deposited by mid-frequency magnetron sputtering

• The nanotribological properties of amorphous carbon nitride (a-CNx) thin films deposited with mid-frequency magnetron sputtering (MFMS) were investigated at the nanoscale using an in-situ technique in a Hysitron Triboindenter TI 950. The friction coefficient, wear rate, track roughness, and the track profiles were recorded as a function of the number of linear reciprocal cycles, revealing the manner that the nanotribological and surface properties change during the wear test. The surface composition of  the films was evaluated by x-ray photoelectron spectroscopy (XPS). The friction coefficient ranges between 0.05 – 0.07, while the wear coefficient ranges from 9.4 x 10-8 up to 1.5 x 10-4 mm3/Nm. Debris particles and surface modifications characterize the friction and lubrication behavior in the track. The friction and main lubrication mechanism on the modified surface changes after the removal of debris particles, while this change appears at different cycle for each CNx film depending on the substrate bias voltage. Films grown at higher bias are modified earlier than films grown at lower bias. The wear behavior can be divided into two, track roughnessdependent, regimes; (1) films with track roughness > 1 nm showed wear with obvious tracks and (2) the films with roughness < 1 nm showed negative wear at the nanometer scale with a volume of material projected in the area of the wear track. This material volume is believed to be result of a surface modification, where the molar volume of the modified surface is larger than the molar volume of the surface before the wear test.

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NATURVETENSKAP  -- Fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences (hsv//eng)

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