Nano additive CeO2 without sulfur and phosphorus was used in combination with molybdenum dithiocarbamate (MoDTC) to solve the problems of low load-bearing capacity and unsatisfactory ...friction-reducing property of organic molybdenum in lubricating grease. By using quartz crystal microbalance (QCM) to analyze the adsorption behavior of the composite additive, it was found that the viscoelastic co-adsorption behavior of MoDTC and CeO2 nanoparticles significantly improved the adsorption rate and equilibrium adsorption mass, which made the PB value of the composite additive increased by 77.6 % and 12.6 % compared with CeO2 and MoDTC, respectively. In the tribofilm formed by composite additive, CeO2 nanoparticles that do not undergo frictional chemical reactions with MoDTC form a flat and hard intermediate layer in the tribofilm, which improves the bearing capacity and effectively suppresses the fluctuation and accumulation of layered MoS2 on the surface. The layered structure is concentrated on the surface of the tribofilm and parallel to the friction direction, significantly reducing the sliding resistance between layers. Therefore, a thinner MoS2 layer with appropriate orientation is more conducive to improving the friction reduction performance of the grease. This results in a 33.9 % decrease in the friction coefficient of organic molybdenum, while its load-bearing capacity increases from 900 N to 1400 N, enabling lithium complex grease to achieve low friction, low wear, and high load simultaneously.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Lubricants are commonly used in manufacturing processes, such as rolling and drawing, to protect contact surfaces in a relative movement against friction and wear. Currently, there are few studies on ...fluid lubricants for the fabrication of large-scale Mg alloy components at high temperatures in the open air. This paper aims to design a type of silicone oil based Al2O3 nano lubricant and investigate its effect on the tribological performance of Mg AZ31B sliding against 86CrMoV7 steel under elevated temperatures with the aid of the pin-on-disc experiments. It was found that the width and depth of the wear tracks at 250 °C are dramatically reduced when the concentration of the Al2O3 nanoparticle additives reaches 0.50 wt% and above, and that there is a strong correlation between the wear rate and average friction coefficient. The investigation revealed that the lubrication mechanism for the contact pair using pure silicon oil at 100 °C is due to the formation of a Si-rich tribofilm, whereas the lubricant with Al2O3 nanoparticles provides a more stable Al-rich anti-wear surface at higher temperatures in the range of 200–250 °C.
•Identified a type of silicone oil based Al2O3 nano lubricant that can minimise surface damage of Mg alloys during contact sliding.•Identified the applicability of the new nano lubricant at temperatures from RT to 250 °C in an open system.•Identified the lubrication mechanisms under elevated temperatures through the analysis of wear tracks.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The effect of atmospheric gas on zinc dialkyldithiophosphate (ZDDP) tribofilm formation was investigated. Macroscale friction tests and in-situ atomic force microscopy (AFM) observations were carried ...out in both normal air and argon. In argon, the tribofilms grew slowly although the initial formation stages were similar to those of ones formed in normal air. Furthermore, after prolonged friction, the tribofilms gradually became smooth and wore away. Oxygen in the lubricant is thus important for ZDDP tribofilm formation, and a sufficient supply of oxygen is necessary to maintain the anti-wear performance of ZDDP.
•The effect of atmospheric gas on ZDDP tribofilm formation was investigated.•ZDDP tribofilm formation in argon was visualised using in-situ AFM observation.•ZDDP tribofilms formed in argon were prone to wear.•They had longer polyphosphate chains and a high sulphur rate.•A sufficient supply of oxygen is necessary to maintain the anti-wear property of ZDDP.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The tribological behaviors of various oxide nanoparticles, i.e. Bi2O3, CuO, SiO2 and ZrO2, added into a carbon fibers reinforced polyether-ether-ketone were comprehensively investigated. It was ...demonstrated that nanoparticle types played an important role in the tribological performance. When sliding took place at a low FV (load×speed) condition, the addition of CuO and ZrO2 nanoparticles led to the formation of patch-like tribofilms increasing friction and wear. However, at FV factors ranging from 30 to 300Nm/s, the hard nanoparticles, i.e. SiO2 and ZrO2, resulted in dramatic improvement of the tribological properties. Moreover, nano-ZrO2 was significantly more effective than nano-SiO2 for enhancing the tribological performance. Hard nanoparticles released onto the sliding interface removed the tribo-oxidation layer on steel counterface. Hereafter, they were “tribo-sintered” into an oxide-based tribofilm having a high load-carrying capability. However, the soft nanoparticles, i.e. Bi2O3 and CuO, did not help to form a robust and lubricating tribofilm.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
A coating composed of Au/Ag/Cu was deposited onto steel surfaces to catalyze the tribochemical reaction of polyalphaolefin (PAO), resulting in the formation of amphiphilic molecules. The coated ...surface showed a reduction in friction coefficient and wear track width by 24.9∼43.0% and 61.4∼68.9%, respectively, compared to the bare steel surface. The in situ formed amphiphilic molecules were chemically bonded on tribopair surface after deprotonation, and then formed a tribofilm. This tribofilm exhibited low interfacial adhesion at nano scale, contributing to low friction and wear. Density functional theory simulations reveals that the dissociation energy of C-H bond on Au surface was much lower than that on iron surface, favoring the catalytic oxidation reaction of PAO into amphiphilic molecules.
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•The synergistic effect of metal coating and liquid lubricant has been achieved to recude friction and wear.•The catalytic effect provided by the tribopair surface has been revealed.•The compatibility between tribopair surface and liquid lubricant has been revealed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Recently, glycerol has raised great interest among researchers as an environmentally-friendly lubricant. Low friction, even super-lubricity, can be achieved when glycerol is used with diamond-like ...carbon coatings. Though TiN coatings are currently widely used in improving the tribological performance of forming tools, cutting tools, and machine elements, no literature exists on the tribological performance of a PVD TiN coating under glycerol lubrication. This paper investigates the combination of TiN coatings with glycerol. The results show that glycerol exhibits excellent lubrication performance, which is stronger in the steel/TiN than in the steel/steel tribopair. The action mechanism of glycerol in steel/TiN tribopair is also proposed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Polymer composites are common materials for tribological components, even at relatively high operating temperatures. One advantage is the possibility to add low friction additives, such as PTFE, to ...the base material. In this paper the influence of such additives was studied, with focus on surface and sub-surface damages. The polymer composites were PPS with glass fibers (PPS-F), PPS with glass fibers and PTFE (PPS-L) and PEEK with carbon fibers, graphite and PTFE (PEEK-L). A reciprocating ball-on-disc test set-up, with ball bearing steel balls as counter material, was used with 5 N and 15 N normal load. The tests were run for 2,000 and 10,000 cycles in room temperature, 80 °C and 120 °C. PPS-F showed high friction (µ ≈ 0.4–0.5) and severe surface damage of both the polymer and the counter surface. Sub-surface cracks, detachment of fibers from the polymer and a deformed surface layer was revealed, when studied in cross section. The load and temperature had negligible effect on the friction, however a higher temperature resulted in more surface damage of the PPS-F. PPS-L and PEEK-L showed relatively low friction (µ ≈ 0.1) and superficial surface damage. XPS analysis revealed a thin tribofilm of PTFE in the wear track for PPS-L.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
We have synthesized two novel amide-based organic friction modifiers(OFMs), namely NIPAOA and NDEAOA, through the addition reaction of oleamine with N-isopropylacrylamide and N, N-dimethylacrylamide. ...The two OFMs exhibit good solubility in PAO6 base oil. Their tribological performance has been investigated using a line contact both individually and when compounded with the anti-wear additive zinc dialkyldithiophosphate (ZDDP) at temperatures ranging from 40 ℃ to 130 ℃. The results show that NIPAOA and NDEAOA form dual-site adsorption on the tribo-pair surface through the N and O atoms in the head group amide, resulting in the tribo-film exhibiting excellent friction-reducing performance in PAO6 across the temperatures. When compounded with ZDDP, they both exhibit effective synergistic friction-reducing effects, attributed to the formation of a unique tribo-chemical reaction film on the worn surface that contains almost no Fe and its compounds. The formation of the unique tribo-film is partly due to the continuous adsorption of free OFMs on the surface of the formed ZDDP tribo-film, providing a milder contact environment for the tribo-pair, allowing for the continuous polymerization of medium and long-chain zinc dialkyldithiophosphate (ZDDP) to ultimately form a uniform and flat tribo-chemical reaction film which interspersed with nitrogen-containing compounds. Even after long-term testing, the film maintains good stability and abrasion resistance, effectively synergizing friction-reducing and anti-wear properties.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
To improve the antiwear properties of halloysite nanotubes as an oil-based additive, the effect of thermal activation on the tribological properties of halloysite was investigated. The results showed ...that the anti-wear properties of the halloysite and calcined products are improved by 34.54% and 45.45 –54.76%, respectively, compared with the base oil. The outstanding wear resistance of the surface lubricated by the calcined product is attributed to the faster and easier formation of a multilayer nanocrystalline tribofilm, which mainly contains the nanocrystalline transition layer, the oxide film (composed of nanoscale iron oxide, Al2O3, SiOx) and the amorphous carbon film. The findings here provide new insights into optimizing the tribological properties of phyllosilicate and enrich the tribological mechanism of halloysites.
•The crystal structure changes of halloysite after thermal activation were studied.•The anti-wear property of calcined products was superior to halloysite.•Thermal activation promoted halloysite to form tribofilm.•The tribofilm contained a multi-layer structure and is nanocrystalline.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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