Abstract:Surface reactive additives are crucial in the lubrication of surfaces experiencing cyclic contact. The combination of additives in the lubricant, on the material surface and the complex tribo-contact conditions hinders the design of additive packages which can simultaneously protect steel surfaces from wear and fatigue. Amine-based Organic Friction Modifiers (OFMs) influence the tribological performance of steel surfaces. This study investigates the tribochemical impact of three amine-based OFMs in combination… Show more
“…55 Additionally, O1s peak at 533.4 ± 1 eV for ZDDP + base oil can be assigned to BO, which links phosphate groups together to form phosphate chains such as metaphosphates (P 2 O 6 ), providing antiwear property to tribofilm. 56 Figure 13.XPS analysis of the worn surfaces.…”
Zinc dithiophosphate is the most commonly used antiwear additive in lubricating oil. However, zinc dithiophosphate has a poisoning effect on engine catalysis via phosphorus and zinc content that reduces the efficiency causing hazardous emission increase, therefore, it needs to be replaced with an alternative additive. In this study, the antiwear performance of molybdenum disulfide (MoS2) is enhanced by zinc sulfate (ZnSO4) addition and subjected to tribometer tests at different contact pressures to explore the MoS2 + ZnSO4friction and antiwear performance against MoS2and zinc dithiophosphate. Wear rates and surface morphology changes were carried out by an optical microscope, optical profilometer, and atomic force microscope analysis. Furthermore, tribochemical and surface energies of tribofilms were evaluated via scanning electron microscope/energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscope adhesion force mapping analysis. Results showed that ZnSO4addition to MoS2 + base oil improves the antiwear performance of the lubricating oil significantly and it presents similar friction characteristics to zinc dithiophosphate.
“…55 Additionally, O1s peak at 533.4 ± 1 eV for ZDDP + base oil can be assigned to BO, which links phosphate groups together to form phosphate chains such as metaphosphates (P 2 O 6 ), providing antiwear property to tribofilm. 56 Figure 13.XPS analysis of the worn surfaces.…”
Zinc dithiophosphate is the most commonly used antiwear additive in lubricating oil. However, zinc dithiophosphate has a poisoning effect on engine catalysis via phosphorus and zinc content that reduces the efficiency causing hazardous emission increase, therefore, it needs to be replaced with an alternative additive. In this study, the antiwear performance of molybdenum disulfide (MoS2) is enhanced by zinc sulfate (ZnSO4) addition and subjected to tribometer tests at different contact pressures to explore the MoS2 + ZnSO4friction and antiwear performance against MoS2and zinc dithiophosphate. Wear rates and surface morphology changes were carried out by an optical microscope, optical profilometer, and atomic force microscope analysis. Furthermore, tribochemical and surface energies of tribofilms were evaluated via scanning electron microscope/energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscope adhesion force mapping analysis. Results showed that ZnSO4addition to MoS2 + base oil improves the antiwear performance of the lubricating oil significantly and it presents similar friction characteristics to zinc dithiophosphate.
“…The iron spectra (PU/PFPE in Figure 8b and LiC/Syn+M in Figure 8f) consists of 2 main peaks with Fe2p 3/2 at 710.81eV and Fe2p 1/2 at ~724.58eV. The lower binding energy of ~707.20eV is assigned to iron disul de (FeS 2 ) [36][37][38]. The main component at ~710.3eV is the peak from iron oxide (Ш) [31,34,35].…”
Section: Xps Analysis Of Tribo Lmsmentioning
confidence: 99%
“…For both greases, the lower binding energy at ~529eV are assigned to zinc and iron oxide, followed by the peak which is assigned to metal hydroxides at ~531.3eV [31,34,38]. Two peaks at higher binding energies (~533-535eV) are further separated into (1) non-Bridging-Oxygen (NBO) peak possibly originating from sulfate (SO 4 ), SiO 2 or hydroxides as well as (2) a Bridging-Oxygen (BO) peak linked to water [31,32,36,37]. In the case of S 2p, one stronger peak was detected at 161.8eV and it was assigned to the sul de group, where the weak peak at 167.9eV was assigned to the sulfate group [32,35,37].…”
Four commercial greases with various thickeners and base oils were experimentally examined to compare their false brinelling wear resistance in a test rig simulating roller bearings during rail/sea transportation for the first time. Greases containing zinc dialkyl dithiophosphates (ZDDP) showed superior false brinelling reduction, evidenced by no visible wear mark in the raceways. The mechanism for false brinelling mitigation was shown to be from a ZDDP-induced tribofilm which decreases the friction and wear coefficient in the contact area. Surface chemical analysis showed that for grease lubricated fretting contacts, ZDDP-derived tribofilms can be generated in the presence of micro-sliding motions and energy dissipation at the contact interface at low frequency (i.e. 4-8 Hz), due to the mechanochemical reactions. For greases without ZDDP, false brinelling wear was reduced by 97% when using grease with a more abundant and less viscous oil, which bleeds readily from an open structured thickener. The results highlight the ability of ZDDP as an additive in grease to better protect roller bearings against false brinelling during rail/sea transportation.
“…In (2), the substrate exerts a repulsive force on the probe, although this does not necessarily mean that the probe contacts the substrate. Curve (3) shows the process in which the probe is released by or recedes from the substrate. The photodetector voltage becomes negative when the restoring force of the cantilever becomes larger than the attractive force between the probe and substrate.…”
Section: Force Mesurementmentioning
confidence: 99%
“…FMs are classified as either reaction film FMs (RF-FMs) or adsorption film FMs (AF-FMs). RF-FMs reduce friction by chemically reacting with the metal surface and forming a coating film [2,3]. Zinc dithiophosphate and molybdenum dithiocarbamate are classified as RF-FMs.…”
There are two types of friction modifiers (FMs) used as lubricant additives: Reaction film FMs (RF-FMs) and adsorption film FMs (AF-FMs). While RF-FMs provide good performance in severe conditions, AF-FMs excel in mild conditions. This empirical evidence leads us to combine these two FMs to cover broader conditions. However, the effects of their combination are highly complicated due to the interaction between these FMs. If the interaction force of AF-FMs with various materials can be evaluated, it would help us to improve tribological performances of lubricants. Although atomic force microscopy seems suitable for this application, we found some obstacles, such as fluid resistance, electrostatic force, and laser positioning of the cantilever, to achieve proper measurements of the adsorption force. In this study, the adsorption force between the polar group and the surface was directly measured in oil with a 1 µm silica probe modified with CH3 or COOH. This paper proposed how to eliminate errors included in the adsorption force measurement using AFM and a calibration method for obtaining an accurate adsorption force of the polar group, and a test of normality of the measured data was conducted by 400 measurements. As a result, it was shown that approximately 100 tests were needed to obtain an accurate adsorption force in this study.
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