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WS and WS/Zr self-lubricating soft coatings were produced by medium-frequency magnetron sputtering, multi-arc ion plating and ion-beam-assisted deposition technique on the cemented carbide YT15 (WC + 15 % TiC + 6 % Co) substrates. Microstructural and fundamental properties of these coatings were examined. Sliding wear tests against 40Cr-hardened steel using a ball-on-disk tribometer method were carried out with these coated materials. The friction coefficient and wear rates were measured with various applied loads and sliding speeds. The wear surface features of the coatings were examined using SEM. The results showed that the WS-1 specimen (with WS/Zr composite coating) has higher hardness and coating/substrate critical load compared with that of the WS-2 specimen (only with WS coating). The friction coefficient of WS-1 specimen increases with the increase in applied load and is quite insensitive to the sliding speed. The wear rate of the WS-1 specimen is almost constant under different applied loads and sliding speeds. The WS-1 specimen shows the smallest friction coefficient and wear rate among all the specimens tested under the same conditions. The WS-1 specimen exhibits improved friction behavior to that of the WS-2 specimen, and the antiwear lifetime of the WS coatings can be prolonged through adding Zr additives. The self-lubricating and wear mechanism of the WS/Zr coating was also found from the sliding wear tests. [ABSTRACT FROM AUTHOR]

Formulae are derived from first principles which predict the wear depth of a ball and a flat surface through time as they slide against each other, in relation to any phenomenological law for wear volume, and taking into account the effect of component geometry. The equations can be fit using experimental wear volume data from ball-on-flat tribometers. The formulae remove previous limiting approximations made in the literature and extend to the prediction of the wear depth of both contacting surfaces. The wear model accords with a previous model that is validated by pin-on-disc testing of a steel/steel contact. The current paper uses the formulae derived to predict the wear depth of a diamond-like carbon (DLC) coating and a steel ball as they slide against each other in deionised water. An Archard equation is used to predict the wear volume of each surface; however, a DLC coating is known to form a transfer layer which reduces the rate of wear, and since this scenario does not obey Archard's law directly, a time-dependent-specific wear rate is used to fit a semi-empirical model to experimental results. The final model predicts the wear depth of the ball and flat accurately. [ABSTRACT FROM AUTHOR]

A new series of novel dicationic symmetrical and asymmetrical ionic liquids (ILs) consisting of tributylalkyl phosphonium and alkylimidazolium were synthesized. Their tribological properties in the form of spin-coated ultra-thin films sliding against AISI-52100 steel ball were studied in a ball-on-plate configuration on a Universal Micro-tribometer-2MT tester, using perfluoropolyether (PFPE) and normal ILs as comparisons. The best result is obtained for asymmetrical 1-(1-tributylphosphine-yl-hexyl)-3-methylimidazolium dihexafluorophosphate, which has very high decomposition temperature-about 450??C and good tribological properties. [ABSTRACT FROM AUTHOR]