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- AFM (1)
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Main focus was on the deposition of carbon nanofibers (CNFs) onto the hard nanocomposite (nc-Ti1 - xAlxN)/(a-Si3N4) (nACo®) coating surface and the investigation of the structure and tribological properties of CNFs. The alcohol chemical vapor deposition (ACCVD) method was employed to prepare CNFs and the deposition temperatures were 600 and 700 °C, respectively. Prior to the CNF deposition, Ni catalyst was deposited onto the nACo® surface using the magnetron sputtering. The influence of the deposition temperature on the carbon nanofibers structure was investigated by Raman spectroscopy and scanning electron microscopy (SEM). The higher order degree of CNF structure is observed with increasing deposition temperature. Tribological tests were carried out under fretting contact conditions against Al2O3 ball. It is shown that the coefficient of friction (COF) decreases from 1.0 to 1.2 for the clean nACo® surface to 0.2–0.4 for the CNF layers deposited on the nACo® surface. The roughness of the nACo® surface was varied and a higher durability of the CNF layers deposited on the rougher nACo® surface is found.
Main focus was on the correlation of the coefficient of friction (COF) with the geometrical parameters of the surface during early stage of the running-in period. TiN, TiAlN and AlTiN coatings were prepared by using rotating cathode arc evaporation unit. The roughness of the WC-Co substrate Ra ranged from 0.05 to 0.2 µm and the coating thickness was 2.3 ± 0.2 µm. Part of the samples were subjected to the surface modification by the drag grinding finishing. Geometrical parameters of the surface were evaluated by means of atomic force microscopy (AFM) and fretting tests were conducted with 10 mm diameter alumina ball under 2 N load, 100 µm slip distance and the frequency of 10 Hz. It was found that the distribution of macroparticles strongly influences the geometrical parameters of the surface and the number of macroparticles increases with increasing Al content in the coating. In the case of the positive skewness Ssq of the coating surface, the kurtosis Sku provides a statistically significant effect on the COF, namely the COF depends inversely on the kurtosis Sku. The kurtosis value for TiN was the highest among as-deposited coatings, subsequently, the slowest increase rate in the COF was observed for the TiN coating.