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Biolubricants are becoming interesting alternatives to mineral lubricants. Despite their advantages, development of lubricants from vegetable oils may compete with food production, turning their use impractical due to socio‐economic aspects. Here, cardanol is used as raw material in the synthesis of novel biolubricants under environmentally friendly conditions. These compounds are characterized by NMR and Fourier transform infrared spectroscopy. Thermal‐oxidative studies show the elevated stability and higher onset oxidative temperatures. Tribological analyses performed under high‐frequency linear‐oscillation motion indicate lower coefficients of friction and wear rates compared to a synthetic oil. Therefore, cardanol, under simple, fast, and sustainable processes can be transformed into valuable alternatives for petroleum‐based lubricants. Practical Applications: The novel cardanol‐based biolubricants presented in this work show interesting chemical and lubricity properties superior to standard synthetic oils, which make them potential substitutes for the current oil‐based products used as lubricants. Additionally, the ecofriendly methodologies employed reduce significantly the reaction time as well as eliminating the need for catalysts or solvents, making these processes viable alternatives for the traditional methods reported in literature for the synthesis of this class of compounds. [ABSTRACT FROM AUTHOR]

Byline: Cristian Viafara, Amilton Sinatora In this paper, a review of the thermodynamic approaches of sliding wear is presented. These approaches are divided into the friction energy dissipation, the energy balance and the entropy production. A concise and critic account of the approaches is discussed, remarking their relative strength and weakness in explaining the phenomena occurring in the sliding wear.

Lubricant oil can be regarded as a complex mixture of base oils and additives, each one with its specific functions and behaviour. In this paper, the interaction of a molybdenum dialkyldithiocarbamate (MoDTC)-based additive and combinations of a polyalphaolefin and a synthetic ester is investigated. A reciprocating ball-on-disc configuration was used for tribological tests. The effect of MoDTC is seen as a sharp drop in the coefficient of friction. This friction reduction is affected by the base fluid: the effect is more intense and lasts longer when the ester content is decreased. The applied normal force also affects the MoDTC effect, which is not sustainable at higher loads. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

ABSTRACT This paper aims to investigate the effect of varying the hardness of both sliding bodies on the operating wear regime. Unlubricated sliding wear tests were performed using a pin-on-disc configuration. The friction coefficient was monitored during the wear tests, and the variation of mass loss of bodies as a function of sliding distance was obtained to estimate the steady-state wear rate. The results showed that the operation of mild and severe wear regimes was influenced by the initial hardness of materials. Under the high pin hardness conditions, a decrease in the disc hardness promoted the severe wear regime operation prior to the action of a mild wear regime. Under the low pin hardness conditions, a severe wear regime was established. When the harder disc was tested, a mild wear regime was observed. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

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Abstract: In a ball-on-disc wear test, an alumina ceramic body sliding against a silicon nitride ceramic body in water achieved an ultra-low friction coefficient (ULFC) of 0.004. The profilometer and EDX measurements indicated that the ULFC regime in this unmated Al2O3–Si3N4 pair was achieved because of the formation of a flat and smooth interface of nanometric roughness, which favored the hydrodynamic lubrication. The triboreactions formed silicon and aluminum hydroxides which contributed to decrease roughness and shear stress at the contact interface. This behavior enables the development of low energy loss water-based tribological systems using oxide ceramics. [Copyright &y& Elsevier]

Abstract: This work presents a study on the influence of residual stresses on the contact fatigue resistance of a gray cast iron and a ductile iron. Contact fatigue tests were conducted in a ball on washer machine. The specimens were taken from bars of gray and ductile iron produced by continuous casting. After machining, specimens of both materials were quenched and tempered to the same matrix hardness, of about 800HV. Two different test configurations were used: (1) regular washers and (2) reduced washers. Specimens in the first group were tested without the imposition of an external force and those from the second group were assembled in a die, which was tightened to a preset level of deformation, so that the induced external stresses could be representative of the presence of residual stresses during the tests. All tests were conducted until the occurrence of spalling, under lubrication and with a maximum Hertz contact pressure of 3.6GPa. Finite element modeling was used to analyze the level and distribution of the imposed stresses. Results showed that the imposition of compressive residual stresses did not alter the fatigue life of gray iron, but increased life scatter for ductile iron. [Copyright &y& Elsevier]

This work evaluates the tribological behavior of three samples taken from a pearlitic steel rail with different hardness values (550, 450 and 370 HV 0.1) due to the in-service work hardening effect. A pin-on-disc sliding wear test was selected to simulate the sliding wear conditions among the wheel flange and rail head corner and gauge face. The influence of the stress level was evaluated by varying the applied normal loads; the 50 and 500 N loads were associated with large and small radius curves, respectively. Pins were made from the rail samples, and the counter body (disc) used was H-13 steel (600 HV30). The mass loss was measured, and the coefficient of friction (COF) for each condition was calculated. Scanning electron microscopy (SEM) was carried out for microstructural characterization of the samples before and after the sliding wear test. The results showed a monotonic correlation between the superficial hardness and the sliding wear resistance under the low severity condition. The sample with the intermediate hardness (450 HV 0.1) has the greatest sliding wear resistance under the low severity, 50 N condition, and under the high severity test condition (500 N). For the tests performed at 50 N, the wear facilitated crack propagation, and the preexisting cracks were removed from the pin (rail) interface. In contrast, for the tests performed with a 500 N load, the material removal rate did not overcome the crack propagation. In addition, the energy at the sliding interface was enough to promote a white etching layer (WEL), which reproduced the surface of the in-service rails, and the material removal was not sufficient to remove the cracks from the pin (rail) surface. • Laboratory test conditions reproduce the microstructural changes in curved tracks of heavy haul railways. • The energy at the sliding interface with a high normal load (500 N) produces a white etching layer. • To increase the service life of rails, it is essential to control the corner microstructure evolution. • Correct grinding procedure at the rail corner is necessary to increase the service life. [ABSTRACT FROM AUTHOR]