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Proteins can adsorb on the surface of materials, such as soft contact lenses (SCLs), and can affect the hydrophobicity, roughness, and surface properties of the contact lenses (CLs), which, in turn, can influence the friction between the lenses and the ocular surface. Excessive friction between contact lenses and the ocular surface can lead to discomfort for the wearer and may cause irritation or inflammation of the cornea, better known as corneal ulcers (keratitis). Bovine Serum Albumin (BSA) is often used as a standard protein in biocompatibility testing of materials, including contact lenses. One standard commercial contact lens was tested under lubricated conditions to access the coefficient of friction (CoF). The contact was lubricated with a tear-like fluid (TLF) solution containing six different concentrations of BSA. In all cases, good linearity of the results of the friction force was verified, suggesting that the first friction law can be applied to determine the value of the coefficient of friction. It was found that friction increases with the increase in protein concentration. [ABSTRACT FROM AUTHOR]

The coefficient of friction for different contacting materials against skin is mainly influenced by the nature of the materials (synthetic and natural fabrics), mechanical contact parameters (interfacial pressure and sliding velocities), and physiological skin conditions (ambient humidity and skin moisture content). In the present research work, seven different types of papers used in everyday life were analyzed. The physical properties of these materials were determined through tensile tests and friction tests. By comparing mechanical properties with coefficient of friction, it was possible to conclude that the coefficient of friction is strongly correlated with the mechanical properties. [ABSTRACT FROM AUTHOR]

Diamond-like carbon (DLC) coatings are widely used in industries that require high durability and wear resistance, and low friction. The unique characteristics of DLC coatings allow for the possibility of creating adsorption sites for lubricant additives through the doping process. In this study, the combined use of europium-doped diamond-like carbon (Eu-DLC), gadolinium-doped diamond-like carbon (Gd-DLC), and pure DLC coatings and an ionic liquid (IL) additive, namely, trihexyltetradecylphosphonium bis (2-ethylhexyl) phosphate [ P 66614 ] [DEHP], with a 1 wt.% concentration in polyalphaolefin (PAO) 8 as a base lubricant was investigated. Higher hardness, higher thin-film adhesion, a higher ratio of hardness to elastic modulus, and a higher plastic deformation resistance factor were achieved with the Gd-DLC coating. The CoF of the Gd-DLC coating paired with the IL was superior compared to the other pairs in all lubrication regimes, and the pure DLC coating had a better performance than the Eu-DLC coating. The wear could not be quantified due to the low wear on the surface of the DLC coatings. The friction reduction demonstrates that tribological systems combining Gd-DLC thin films with an IL can be a potential candidate for future research and development efforts to reduce friction and increase the efficiency of moving parts in internal combustion engines, for instance. [ABSTRACT FROM AUTHOR]

Cemented carbides are highly resistant to abrasion, erosion and sliding wear and are frequently used in drilling and cutting tool operations. In the present investigation, different submicrometric (0.8 µm) WC (tungsten carbide)-based composites were developed, containing various binders of Co, Ni, NiCr, NiMo, and NiCrMo. The main objective of the work was simultaneous tribological and electrochemical characterization to investigate the mechanisms of surface degradation when subjected to mechanical wear and how they interconnect with chemical or electrochemical processes and each other. By comparison with previous tribological tests, under dry sliding and the same contact conditions of load and frequency, it can be concluded that a synergistic effect was not observed and that the solution works mainly as lubrication, resulting in increased combined wear–corrosion resistance. [ABSTRACT FROM AUTHOR]

Tungsten carbide-based composites are, in many cases, the materials of choice in applications requiring high wear resistance. In the present research work, the mechanical characterization of the WC-Co and WC-AISI 304 composites was carried out, with evaluation of the hardness and fracture toughness and tribological characterization of the composites that included the study of friction and wear rate coefficient through unlubricated sliding tests according to the Pin-on-Disc test method. It was possible to correlate the effect of the different binding phases on the mechanical and tribological properties of WC-based composites, and it can be concluded that the system composed by the tribological pair WC-AISI304/100Cr6 was the one that showed the lowest coefficient of friction while the tribological pair WC-Co/Al2O3 was the one that showed the lowest wear rate coefficient. [ABSTRACT FROM AUTHOR]

The present research paper aims to evaluate the tribological behavior of coatings in applications where high wear resistance and low friction are required, commonly used in refurbishment of various items of industrial equipment. Twelve tribological pairs made of six different coatings, corresponding to three different coating families, have been studied: TiSiN, Cr, and DLC (diamond-like carbon). The coatings were produced using a technique called high power impulse magnetron sputtering (HiPIMS). To perform the tribological tests, two methods were used to measure friction, namely energy dissipation in vibratory systems and sliding indentation. The first technique is based on the evaluation of free vibration movement with damping of a mass–spring system induced by a mechanical impulse where the contact between the vibrating device and the sample to be analyzed acts as an additional energy dissipation. At the same time, friction is determined through the inverse analysis by comparing the experimental vibratory movement with the analytical equation of the movement. The determination of the load-bearing capacity of the various coatings has been evaluated using sliding indentation tests against spherical bodies using a constant sliding speed and increasing normal loads. The results obtained in both tests allow to verify a relationship between the friction coefficients of the studied tribological pairs: µDLC < µTiSiN < µCr. This relationship does not occur in the case of the vibration test with the 100Cr6 counter-body. [ABSTRACT FROM AUTHOR]

Modifying the surface of materials through texturing and coating can have a significant impact on their tribological properties. In the present study, a hybrid surface modification process, texturing combined with coating, has been applied to a steel surface and the tribological behavior in lubricated conditions was studied. The surface of the steel was textured using micro-electric discharge machining (micro-EDM) to create two distinct patterns (rectangular and circular). Following this, transition metal dichalcogenides (TMD); tungsten-sulphur‑carbon (WSC) coating was applied to the surface using magnetron sputtering. To evaluate the specimens, they were subjected to tribological testing in various lubrication conditions using a block-on-ring configuration. The results were corroborated using a reciprocating sliding test and compared to those of a smooth uncoated specimen. The findings revealed that the tribological properties of the textured and coated specimens were enhanced, particularly in specimens with circular dimple patterns. The WSC coated circular dimple specimens showed a reduction of the COF by 7–12 %, in the boundary lubrication regime and by 9–25 %, in the mixed and hydrodynamic lubrication regimes as compared to the untreated specimen. • M2 substrate was modified by EDM texturing and WSC coating originating a hybrid surface. • Two hybrid surfaces were produced, one with rectangles and another with circles. • Two different contact conditions: block-on-ring and pin-on-disc showed the same trend in friction. • Synergic effect of texturing plus coating compared with smooth and uncoated specimens was obtained. [ABSTRACT FROM AUTHOR]