Search

Molybdenum dialkyldithiocarbamate (MoDTC) is widely used as a friction modifier in engine lubricating oil. Under MoDTC lubrication, the friction and wear behaviors of tungsten-doped diamond-like carbon (W-DLC) films annealed at 100–400 °C were discussed and evaluated using scanning electron microscopy (SEM), atomic force microscopy (AFM), and Raman spectroscopy. Under (polymerized alpha olefin) PAO + MoDTC lubrication, the coefficient of friction of all samples decreased, but the wear rates of the W-DLC films annealed at 300 °C increased significantly. By interacting with zinc dialkyldithiophosphate (ZDDP), the wear rates of W-DLC films annealed at different temperatures declined significantly owing to the formation of dense phosphate tribofilms on the worn surfaces. [ABSTRACT FROM AUTHOR]

Some special silicate particles as additives in lubricating oil have shown a certain self-repairing function for the rubbing pairs of industrial equipment in recent R&D of extreme pressure antiwear additives. This article introduces an investigation on the regenerated layer on the worn surface of a practical cylinder liner lubricated by lubricating oil with a silicate additive using some advanced techniques like transmission electron microscopy (TEM), atomic force microscopy (AFM), nano-hardness tester, scanning electron microscopy (SEM), auger electron spectroscopy (AES), and Raman spectroscopy. The basic formula of the mineral in the silicate additive is Al4[Si4O10](OH)4. Through some macro- and microanalyses, it was found that the silicate additive showed an obvious improving effect on their friction surface and self-repairing function. The roughness of the worn surface could be decreased greatly to several tens of nanometers, and its hardness was still above 10GPa. The worn surface with some pits and cracks had been covered by a transparent regenerated layer, and the wear of cylinder liners was maintained at almost zero-wear level on average. The mechanism of the self-repairing function was approached. It was revealed that the silicate additive was acting as a catalyst to promote a series of complex tribochemical reactions to form a regenerated layer with amorphous carbon structure on the worn surface under high-friction temperature and pressure in the friction and wear process. [ABSTRACT FROM AUTHOR]

The synergistic effects between sulfurized-nanocrystallized 316L stainless steel and molybdenum dithiocarbamates (MoDTC) additive under boundary lubrication were investigated in this paper. The tribological behaviors of the treated steel were investigated on a ball-on-disc SRV tribometer. The chemical analysis of tribofilms was performed by X-ray photoelectron spectroscopy (XPS). The results showed that the sulfurized-nanocrystallized sample exhibited the lowest coefficient of friction (0.060) and the lowest wear rate under MoDTC lubrication. The sulfurized ultrasonic cold forging technology (UCFT) composite treatment provided a strong support to the soft FeS layer and prolonged its service time. The MoS 2 decomposed by MoDTC can achieve the lowest coefficient of friction. [ABSTRACT FROM AUTHOR]

Molybdenum dithiocarbamate (MoDTC) is usually added in low viscosity engine oils to improve its ability to reduce friction. However, increasing the amount of MoDTC added results in unwanted sulfated ash increases and other adverse effects. Thus, it is necessary to investigate the optimization of the amount of MoDTC added. The current work investigates this topic in terms of the Mo concentration in the lubricant. Seven different Mo concentrations with the same additive package are tested, whose tribological properties and chemistry of the tribofilm are investigated. For the selected operating conditions in this study, the critical concentration of Mo is determined to be ≈ 350 ppm due to its ability to reduce the friction to ≈ 0.04 under a constant and varying lambda ratio by forming the required threshold thickness of MoS 2 within the tribofilm matrix, dominated by zinc dialkyl dithiophosphate (ZDDP) species. In general, increasing the Mo concentration increases the formation rate of MoS 2 in the initial stages of the traction, directly forming a thicker MoS 2 layer within the tribofilm up to a specific Mo concentration. Induction time also decreases with increasing Mo concentration, and increasing the Mo concentration from 350 to 1000 ppm does not negatively impact the wear generated. • Optimization Mo concentration in a new low viscosity engine oil is investigated. • Mo's critical concentration is determined to be ≈ 350 ppm as it reduces the friction to ≈ 0.04. • Increasing Mo concentration increases the MoS 2 formation rate and decreases induction time. • Increasing Mo concentration from 350 to 1000 ppm does not negatively impact wear. [ABSTRACT FROM AUTHOR]

Abstract: The interactions and synergistic tribological effects between plasma nitrided 52100 steel and molybdenum dithiocarbamates (MoDTC) additive under boundary lubrication were studied in this work. The tribological behaviors of plasma nitrided and untreated steels under lubrication with different MoDTC concentrations were examined on a four-ball friction and wear tester. The results showed an obvious synergistic effect between plasma nitrided steel and MoDTC additive. The synergistic effect indicated a lower friction coefficient without an induction phase and a higher wear resistance, which was attributed to more amount of MoS2 and absorbed carbon were formed in the tribofilm of the nitrided surface. [Copyright &y& Elsevier]

Abstract: Low temperature ion sulfuration technology was used to obtain sulfurized layer on W doped diamond-like carbon (W-DLC) coating. The tribological behaviors of the pure W-DLC and sulfurized W-DLC coatings were investigated under PAO and MoDTC lubrication conditions. It shows that sulfurized W-DLC coatings can obviously improve their tribological performances under PAO with MoDTC lubrication. The primary reason is due to the formation of WS x on the surface of sulfurized W-DLC coating, the decomposition of additives for formation a higher ratio of Mo sulfide/Mo oxide and the graphitization for a high ratio of sp2/sp3. [Copyright &y& Elsevier]