Phase transition of CNx coatings by sliding against a Si 3 N 4 ball has been studied by Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) to understand this super-low friction phenomena in N 2 . A pin-on-disk type tribometer was constructed to determine the tribological properties of this coating when sliding against a Si 3 N 4 ball in N 2 . The analytical results by AES and XPS showed that the nitrogen atoms desorbed from the top layers of the coating, and that the layers changed to a graphite-like structure without nitrogen during a friction coefficient decrease to lower than 0.01. The structural transition of CNx is discussed in this paper.
In this study, amorphous hydrogenated carbon (a-C:H) and Si-doped diamond-like carbon (Si-DLC) films were prepared using microwave sheath voltage combination plasma (MVP) deposition. The thermal stability of the a-C:H and Si-DLC films were investigated by performing an annealing test (100-700ºC) in ambient air. Furthermore, the in situ high-temperature tribological properties on the films were investigated by performing a sliding test against a Si 3 N 4 ball at high temperatures (100, 200, and 300ºC). Hardness measurements and a tribological test showed that Si-DLC has better thermal stability than a-C:H; however, Si-DLC has a higher friction coefficient and undergoes more wear than does a-C:H in the in situ high-temperature tribological test. Therefore, the failure of Si-DLC is due to adhesive wear, whereas that of a-C:H is due to abrasive wear.
ZnDTP antiwear additive for lubricating oil is known to absorb strongly on sliding surfaces in boundary lubricated tribosystems, forming a tribofilm, which is able to reduce the wear of involved surfaces. It is also known to increase the friction coefficient in most DLC/DLC contacts, with the exception of ta-C DLC / ta-C DLC contact, for which the difference in friction behaviors between a base oil + ZnDTP additive lubricated tribosystem and a base oil lubricated tribosystem is not very significant. In this study we investigate a characterization method of the shape of the tribofilm formed on different types of DLC coatings and on the relation between the shape of the tribofilm and the friction behavior of the related DLC coating. Results show that compared to other investigated DLC types, the tribofilm formed on ta-C DLC has some unique characteristic topography features that promote lower friction coefficient.
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