Search

Rotational speed has an important influence on the performance of coating materials. The a-C:Ta composite coatings were prepared by controlling the substrate rotational speed during deposition process using PVD technique. The results showed that the coating transformed from dense structure to columnar structure. Due to the changes of deposition time and the vapor incident angle of the sputtering ions, the sp2 hybrid structure increased and the C–Ta bonds contents decreased as a function of the rotational speed, which led to the improvement of adhesion force. The average friction coefficient of the composite coatings did not fluctuate significantly for the amorphous carbon matrix and the transfer films formed during friction, while the wear rates were gradually increased. The sample at 0.5 rpm possessed the lowest wear rate, which was mainly associated with the cooperative behavior of the dense structure and the formation of TaC nanoclusters in the composite coating. [ABSTRACT FROM AUTHOR]

[Display omitted] • The ultra-low friction is achieved by using the inorganic salts and the proton-based ionic liquid. • The addition of the proton-based ionic liquid and the inorganic salts can enhance the P B value to 3090 N. • The system is suitable for a wide range of applications, including load ranges, sliding speed range and different alcohol types. • The proton ionic liquid not only can be adsorbed on the surface of the friction pairs, but also can form a triple film to get ultra-low friction. • The addition of inorganic salts that can form hydrated molecular layer to withstand high normal loads is the key factor. Macroscale facilitated lubrication is a forward-looking strategy in modern tribology that can significantly reduce friction and wear in mechanical equipment. However, it has been studied experimentally mainly for special friction pairs or point-to-surface contact. In the present work, we have achieved the ultra-low friction for point-to-point contact at the steel/steel interfaces by using the inorganic salts (NaCl and KCl) and the proton-based ionic liquid possessing a simple synthesis step and good solubility stability in aqueous 1,3-propylene glycol (PDO aq). Besides, the addition of the proton-based ionic liquid (PIL) can enhance the maximum non-seizure load (P B value) in PDO aq to 3090 N and the addition of inorganic salts don't lower the P B value. Results show: (1) The proton ionic liquid can be adsorbed on the surface of the friction pairs through electrostatic interactions, and undergo a friction chemical reaction to form a triple film that can effectively cushion the direct contact and collision of the microgrooves. (2) The addition of inorganic salts can form hydrated ions, which can shape a hydrated molecular layer to withstand high normal loads and balance the van der Waals attraction by hydration repulsion, which is a key factor in realizing the ultra-low friction. This discovery greatly expands the application of facilitated lubrication for point-to-point contact on steel surfaces in engineering applications. [ABSTRACT FROM AUTHOR]

In this work, the friction and wear properties of layered MoAlB ceramics sliding against Al 2 O 3 and Inconel 718 alloy (Inc718) from room temperature (RT) to 800 °C were studied. The tribological behaviors of MoAlB ceramics are found to be greatly influenced by the test temperature and the counterpart. From RT to 800 °C, the MoAlB/Al 2 O 3 tribo-pairs exhibit a higher friction coefficient and wear rate compared with those of the MoAlB/Inc718 tribo-pairs. Irrespective of the laminate structure, the tribological properties of MoAlB ceramics are associated with the oxides that are induced by tribo-oxidation reactions. For the MoAlB/Al 2 O 3 tribo-pairs, abrasive wear and adhesive wear are responsible for the poor friction and wear behaviors. However, the tribo-film, which consists of oxides of Ni, Cr and Fe, can provide a good lubrication effect when MoAlB slides against Inc718. [ABSTRACT FROM AUTHOR]

Abstract: In order to lubricate ZrO2 ceramic, a series of ZrO2 matrix high-temperature self-lubricating composites were designed and prepared by hot-press technique. It was found that the ZrO2(Y2O3)–CaF2–Mo–graphite system showed a good tribological behavior at both low and high temperatures. The wear mechanism of the composite was investigated in detail. [Copyright &y& Elsevier]

• Preparation of gallate ionic liquids (GAILs). • Their lubricating performances for copper and aluminum friction pairs are discussed. • The GAILs show prominent friction reduction and wear resistance properties. • The properties are attributed the formed physicochemical adsorbing films. In this study, four kinds of GAILs were prepared and used to lubricate copper and aluminum friction counterfaces. Their physicochemical and tribological properties were systematically investigated. The results showed that the GAILs have better performances with regard to viscosity-temperature characteristic, corrosiveness and hydrolytic stability as compared with the two traditional halogen-containing IL lubricants L-B104 and L-F104. Moreover, the most prominent nature of the GAILs are their excellent friction reduction and wear resistance properties as lubricants for copper and aluminum friction counterfaces, while traditional halogen-containing ILs are generally found to be unsuitable for lubricating these counterfaces. The excellent tribological properties of the GAILs are conjectured to be largely attributed to the physical/chemical adsorbed films formed by the GAIL molecules on the friction surfaces, which is further verified by QCM and XPS analysis results. [ABSTRACT FROM AUTHOR]