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The powders of hBN, SiC, and B4C were employed as the raw ingredients to prepare the B4C–SiC–hBN composite ceramics by a vacuum high-pressure sintering method with hBN and SiC contents in the range of 0, 10, and 20 wt.%, respectively. A pin-on-disc testing equipment was used to assess the tribological properties of B4C–SiC–hBN composite ceramics with various hBN and SiC content when sliding against AISI 347 steel immersed in the emulsion. The experiment's findings indicate that the sliding COF of the B4C/AISI 347 steel pair marginally drops as the sliding distance increases. Besides, the sliding COF of the B4C–10 wt.% SiC–20 wt.% hBN/AISI 347 steel pair rapidly declines. By tribopairs of B4C–SiC–hBN composite ceramics against AISI 347 steel under the condition of lubrication by water-based emulsion, the steady-state friction may move into a state of mix lubrication as the hBN concentration rises, improving the tribological performance. The steady-state COF considerably decreases to 0.01 from 0.386 as the hBN and SiC concentration is increased to 20 wt.% and 10 wt.% from zero, showing a decreasing trend for both the B4C–SiC–hBN pin and AISI 347 steel disc samples' COWs. The steady-state friction of tribopairs of B4C–SiC–hBN composite ceramics against AISI 347 steel may enter a state of mixed lubrication in the emulsion. The wear resistance of composite ceramics was improved by the addition of hBN and SiC particles because of their lubricating and reinforcing effects. These findings offer valuable insights into the design and development of advanced composite ceramics for various industrial applications that require improved tribological properties. [ABSTRACT FROM AUTHOR]

Genetic function approximation (GFA) algorithm was used to model the quantitative structure–activity relationship (QSAR) among corrosion inhibition efficiency, friction coefficient and oil film strength of the thiadiazole derivatives as corrosion inhibitor and antiwear and friction-reducing agent. Corrosion inhibition efficiency, friction coefficient and oil film strength of these compounds on the steel surface contained in the emulsion were studied by weight loss test and a fourball friction and wear test. The results show that quantum descriptors are a better choice for predicting the corrosion inhibition efficiency, friction coefficient and oil film strength of lubricants. For the thiadiazole derivatives, friction coefficient of the lubricants is inversely proportional to their inhibition efficiency and oil film strength. [ABSTRACT FROM AUTHOR]

For the development of national industry green environmental protection, the use of zinc dialkyl dithiophosphate (ZDDP) should be reduced in the process of mechanical lubrication, two novel borate esters, SS-(5-disulfanyl-1,3,4-thiadiazol-2-yl) O-(6-stearoyl-1,3,6,2-dioxazaborocan-2-yl) carbono(dithioperoxoate) (BNSD) and 6-stearoyl-1,3,6,2-dioxazaborocan-2-yl stearate (BNCD), were synthesized and characterized by FT-IR and TGA. Tribological performance of ZDDP, BNSD and BNCD as a multifunctional additive in synthetic ester base oil were investigated under different loads using a MR-S10 four-ball and MFT-3000 friction and wear test machine. A scanning electron microscope and laser scanning confocal microscope were used to observe worn scar surface morphology of the balls. The chemical compositions of worn surface were analyzed by X-ray photoelectron spectroscopy and the tribofilm of the worn surface was observed by transmission electron microscope. The TGA curves showed that BNSD and BNCD had a better thermal stability than ZDDP. BNSD exhibits excellent anti-wear and friction-reducing properties, the PB value is increase to 784 N when the optimized concentration is 0.3% the minimum WSD of BNSD-based lubricant is approximately 0.52 mm and decreased by 35% compared with the base oil. A protective tribofilm of the ball steel was analyzed by XPS and TEM, which revealed that B2O3 and Fe2B constitute the triboilm and about 5 nm. Therefore, BNSD could be a candidate as anti-wear and friction-reducing agent in lubricants instead of ZDDP. [ABSTRACT FROM AUTHOR]

[Display omitted] • Adsorption models of n -hexadecane, tetradecyl alcohol, T309 and EAK on Al (1 1 1) plane were built by DFT. • Confined shear process of the lubricant system mixed with four molecules in Fe-Al system was simulated by MD. • Friction coefficient of the lubricant in Fe-Al system sliding was calculated and measured. Reducing wear and friction coefficient in the process of metal plate processing can save energy. In this work, the quantum chemical parameters of n -hexadecane, tetradecyl alcohol, triphenyl thiophosphate (T309) and dialkyl dithiophosphate (EAK) and the adsorption process on Al (1 1 1) plane were calculated based on density functional theory. The confined shear process of the lubricant system mixed with the above four molecules in Fe-Al system was simulated by molecular dynamics method, and the friction coefficient of the lubricant was calculated. The friction coefficients of lubricants were measured by reciprocating friction and wear test. The results show that T309 has the strongest reactivity and the most stable adsorption, and its adsorption energy on Al (1 1 1) plane is −12.08 eV. Shear force will affect the adsorption morphology of molecules, and long chain molecules will have a certain degree of crimp. When the pressure was 0.5 GPa, the minimum friction coefficient of lubricant was 0.24, mainly because the molecules would gather and adsorb to the metal wall during the shear process. With the increase of pressure perpendicular to the shear plane, the lubricant molecules on the metal wall would gather less, and the distribution of lubricant molecules between the metal walls was gradually uniform. The tested minimum friction coefficient (∼0.12) of the compound lubricant is attributed to synergistic friction reduction among molecules. Based on molecular dynamics simulation, the friction coefficient of aluminum lubricants can be predicted, and the simulated data are accurate and reliable. [ABSTRACT FROM AUTHOR]

Research and development on the high biodegradability of additives is indispensable for environmentally friendly lubricants, which is one of the key factors to advance lubricant technology toward “greener” chemistry. The tribological performance of fatty alcohol polyoxyethylene phosphate acid ester (EK), boron-containing amide (BT), dialkyl dithiophosphate ester (DDE), and a mixture of these (compound) as extreme pressure (EP)/antiwear (AW) additives in hydrogenated base oil (GH) were investigated using a four-ball testing machine. The elemental composition and chemical characteristics of the AW films generated on the surfaces of the steel balls were studied using X-ray photoelectron spectroscopy (XPS), and their AW mechanisms are hereby proposed. Thermal degradation tests were conducted to identify their thermal stabilities using thermogravimetry and differential scanning calorimetry. The results show that these additives can greatly improve the EP/AW properties of GH. XPS analyses of the worn surfaces indicate that decomposed borate esters and organic sulfide or nitrides were adsorbed on the worn surface, and the P and S elements of the compound reacted with the metal and existed in the form of phosphates and sulfates, both of which contributed to the formation of a boundary lubricating film. Moreover, these additives provide the lubricants with excellent oxidation resistance and thermal stability. [ABSTRACT FROM PUBLISHER]