Molybdenum Dialkyldithiocarbamate Research Articles

Synergistic Effect of Acrylate of Dialkyl Dithiophosphoric Acid Combined with Molybdenum Dialkyl Dithiocarbamate as Additives in Gear Oil

With the aim of improving the tribological properties of low-viscosity gear oil for automobiles, an acrylate of dialkyl dithiophosphoric acid (ADDP) with strong polar groups was synthesized. The tribological behavior of ADDP combined with molybdenum dialkyl dithiocarbamate (MoDTC) in gear oil was systematically studied. Tribological performances of gear oil containing different additives were assessed using a four-ball friction and wear tester. The obtained tribological characteristics reveal that ADDP and MoDTC can significantly improve the antiwear and antifriction performance of low-viscosity gear oil. Moreover, compared with using MoDTC or ADDP alone, the average friction coefficient and wear scar diameter of ADDP combined with MoDTC further decreased by 2.41–19.15% and 5.00–18.19%, respectively. Analysis of the worn surface showed that the structural characteristics and physical synergistic lubricating actions of the ADDP with MoDTC additives during the friction process can contribute to the exceptional tribological properties of the hybrid additives.

Revealing the tribological mechanism of synergistic effect between MoDTC and P-containing additives in aluminum-based grease

Purpose This study aims to reveal the tribological mechanism of synergistic effect between MoDTC and P-containing additives in aluminum-based grease. Design/methodology/approach The authors prepared a molybdenum dialkyl dithiocarbamate (MoDTC) and revealed the tribological mechanism of synergistic effect between MoDTC and P-containing additives in aluminum-based grease by combining with ZDDP and P-containing and S-free additives. Findings The MoDTC the authors prepared has good friction-reducing and anti-wear properties in aluminum-based grease and has an obvious synergistic effect with ZDDP. MoDTC and ZDDP have a significant synergistic effect on the tribological properties in aluminum-based grease, mainly because of the formation of phosphates and metaphosphates as well as more MoS2 in the friction film. P element plays a facilitating role in the chemical conversion of MoDTC to MoS2. Originality/value The experiments of MoDTC with tributyl phosphate and trimethylphenyl phosphate confirm that the P element plays a facilitating role in the chemical conversion of MoDTC into MoS2. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-12-2023-0410

Research on the Optimization of Tribological Performance of Wind Power Lubricating Grease Based on Carbon Emission

The manufacturing, installation, operation and dismantling of wind turbines can also have environmental impacts such as excessive carbon emissions and consume large amounts of resources. Optimisation of the tribological properties of wind power greases can reduce the energy consumption and carbon emissions of wind power systems, improve their operational efficiency and reliability, thereby slowing down climate change and improving environmental quality, which is not only important for individual wind power projects, but also has a positive impact on reducing carbon emissions, promoting clean energy development and combating climate change on a global scale. However, the higher the grease lubrication performance, the lower the wind turbine failure rate and the lower the carbon emissions. Good tribological properties can significantly reduce the coefficient of friction of mechanical components, reducing surface wear and heat generation, helping to extend the life of mechanical equipment, improve efficiency and reduce unnecessary repairs and replacements. Therefore, in this paper, Mobil SHC 461WT lithium composite grease was mixed with molybdenum dialkyl dithiocarbamate (RFM3000), nano-boronated rare-earth friction modifiers (SK3115), polysiloxane viscosity modifier (PV611), and zinc dialkyl dithiophosphate (ZDDP), and the comparative analysis of their tribological performances was carried out through the method of cross-experimentation. The results showed that the average coefficient of friction of Mobil added with the four antiwear additives was reduced by 74%, 41%, 54% and 48%, respectively, and the average diameter of wear spots was reduced by 64%, 63%, 69% and 54%.

Effect of additive combinations on tribofilm formation in fully formulated 0W‐8 oil

Reducing engine oil viscosity is an effective way to meet automotive fuel efficiency requirements. Clarifying the effects of multiple coexisting additives in low-viscosity oil is important for the development of low-viscosity engine oil. In this study, six kinds of 0W‐8 engine oil, including those without a Ca-derived detergent, a dispersant or molybdenum dialkyldithiocarbamate (MoDTC), were selected to study the effects of these additives on the tribofilm formation and the friction characteristics of fully formulated low-viscosity oil. A custom-made rolling and sliding tribometer was used to evaluate the tribological properties and form the tribofilms. The elemental distribution of the tribofilms was characterized by electron probe microanalysis (EPMA), and the chemical compositions of the films were determined using X-ray photoelectron spectroscopy (XPS). The Ca-derived detergent hindered both the ZnDTP-derived and MoDTC-derived tribofilm formation in the fully formulated low-viscosity oil due to adsorption competition. The effect of the ashless dispersants on the ZnDTP-derived tribofilm formation in the fully formulated 0W‐8 oil showed opposite results in the presence or absence of MoDTC. The addition of MoDTC had different effects on the ZnDTP-derived tribofilm formation under different additive combinations.

Tribological Properties of Polymer Friction Improvers Combined with MoDTC/ZDDP at Different Temperatures

To expand the applications of polymer friction modifiers in low viscosity oils suitable for hybrid power systems, the tribological properties of five kinds of oil samples at different temperatures were studied, which were compounded with polymer friction modifiers Perfad XG 2500, molybdenum dialkyl dithiocarbamate (MoDTC), zinc dialkyl dithiophosphate (ZDDP). When Perfad XG 2500 is used alone, it forms a brush-like surface film at low temperatures, which can provide lower initial friction. With the rise in temperature, its antifriction effect decreases significantly, which is related to the desorption behavior of physical film. When Perfad XG 2500 is combined with MoDTC, it has the best synergistic antifriction effect, and the average friction coefficient is reduced by a maximum of 20.83% (90 °C). Its friction coefficients decrease significantly with the increase in temperature due to the dissociation process of MoDTC catalyzed by high temperature. However, there are many furrows on the worn surfaces, and the sharp features of the profiles are obvious. When Perfad XG 2500 is combined with ZDDP, it has the best synergistic anti-wear effect, and the total wear depth is reduced by 49.6%. Its worn surface is smooth and defect-free, with minimal residual strain. The friction coefficients are hardly affected by temperature, and the average friction coefficient is reduced by a maximum of 14.4% (30 °C). When Perfad XG 2500, MoDTC and ZDDP are used together, the average friction coefficient is reduced by up to 15.2% (30 °C). Its friction coefficient increases slightly with the rise in temperature. The reason for its moderate tribological performance may be related to the superficial competition of various additives.

Synergistic tribological effect between polyisobutylene succinimide-modified molybdenum oxide nanoparticle and zinc dialkyldithiophosphate for reducing friction and wear of diamond-like carbon coating under boundary lubrication

Organic molybdenum lubricant additive like molybdenum dialkyl dithiocarbamate (MoDTC) can cause wear acceleration of diamond-like carbon (DLC) coating coupled with steel under boundary lubrication, which hinders its industrial application. Therefore, polyisobutylene succinimide (PIBS), an organo molybdenum amide, was adopted to modify molybdenum oxide affording molybdenum polyisobutylene succinimide-molybdenum oxide nanoparticles (MPIBS-MONPs) with potential to prevent the wear acceleration of DLC coating. The thermal stability of MPIBS-MONPs was evaluated by thermogravimetric analysis. Their tribological properties as the additives in di-isooctyl sebacate (DIOS) were evaluated with MoDTC as a control; and their tribomechanism was investigated in relation to their tribochemical reactions and synergistic tribological effect with zinc dialkyldithiophosphate (ZDDP) as well as worn surface characterizations. Findings indicate that MPIBS-MONPs/ZDDP added in DIOS can significantly reduce the friction and wear of DLC coating, being much superior to MoDTC. This is because MPIBS-MONPs and ZDDP jointly take part in tribochemical reactions to form a composite tribofilm that can increase the wear resistance of DLC coating. Namely, the molybdenum amide on MPIBS-MONPs surface can react with ZDDP to form MoS2 film with excellent friction-reducing ability; and MPIBS-MONPs can release molybdenum oxide nanoparticle to form deposited lubrication layer on worn surfaces. The as-formed composite tribofilm consisting of molybdenum oxide nanocrystal, amorphous polyphosphate, and molybdenum disulfide as well as a small amount of Mo2C accounts for the increase in the wear resistance of DLC coating under boundary lubrication.

Low Friction Achieved on Plasma Electrolytic Oxidized TC4 Alloy in the Presence of PAO Base Oil Containing MoDTC

Surface engineering is required to improve the poor lubrication performance of titanium alloys in many applications. In this study, an oxide coating with high-hardness was created on TC4 titanium alloy by using plasma electrolytic oxidation (PEO). The composition and structure of the PEO coatings were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy. The tribological properties of the PEO-treated TC4 were investigated in the presence of a polyalphaolefin (PAO) base oil with addition of molybdenum dialkyldithiocarbamate (MoDTC). The results show that the PEO-treated TC4 exhibits excellent lubrication performance in the presence of MoDTC. The oxide coating on the PEO-treated TC4 sample shows a tribo-induced catalysis effect enabling the decomposition of MoDTC to forms an effective lubricating film containing MoS2, resulting in reduced friction and wear.

HAXPES Study on Chemical States of Reaction Films Formed on Metal Surfaces by Zinc Dialkyldithiophosphate and Molybdenum Dialkyldithiocarbamate

HAXPES Study on Chemical States of Reaction Films Formed on Metal Surfaces by Zinc Dialkyldithiophosphate and Molybdenum Dialkyldithiocarbamate

Probing the Tribochemical Impact on Wear Rate Dynamics of Hydrogenated Amorphous Carbon via Raman-Based Profilometry.

Solid-liquid lubricating systems have received significant attention as a promising way for energy saving and emission control. For deeply understanding their tribological behaviors, it is necessary to study interaction mechanisms between solid and liquid lubricants from the tribochemical viewpoint, as tribofilms formed by tribochemical products on contact surfaces critically affect the whole tribological process. Continually or periodically monitoring tribofilm formation and evolution can contribute significantly to clarifying its dominating role in tribological behavior under boundary lubrication. However, detecting tribofilms in situ remains a big challenge for conventional surface analytical approaches, mainly due to their limitations in accessing tribofilms or low signal intensities of thin tribofilms. In this study, highly sensitive Raman-based profilometry with in situ potential has been developed for detecting molybdenum dialkyldithiocarbamate (MoDTC)-derived tribofilms and exploring their effect on a-C:H wear over time. The optical properties of tribochemical products formed on the coating surface in different wear stages could result in extra attenuation of Raman signal intensities in the form of measurement deviations in wear depth. By monitoring the deviations, key information of tribofilm compositions was obtained and a two-stage wear progression mechanism was proposed for the first time to clarify the detrimental effect of MoDTC-derived tribofilms on a-C:H wear by combining detailed structure and composition analyses.

Suppressed MoO3/FeMoO4 formation in molybdenum dialkyl-dithiocarbamate-derived tribofilms on nitrogen-incorporated Al-Mg-Ti-B coatings

The tribo-chemical interplays between hard coatings and lubricant additives have attracted considerable attentions during recent years. It has been demonstrated that Al-Mg-Ti-B coatings exhibit a good tribo-chemical compatibility with typical lubricant additives zinc dialkyldithiophosphate (ZDDP) and molybdenum dialkyl-dithiocarbamate (MoDTC). Herein, a systematic study was conducted on the tribological behaviors of N-incorporated Al-Mg-Ti-B coatings under MoDTC lubrication. By addition of N in the coatings, TiO2 at the coating surfaces was found to be partially reduced into TiO2−x. Notably, the formation of MoO3 and/or FeMoO4 was shown to be substantially suppressed in MoDTC tribofilms on N-incorporated Al-Mg-Ti-B coatings, resulting in a MoS2-dominated MoDTC tribofilm formed on the coating surfaces. Such interesting tribo-chemical behavior has been tentatively explained in terms of excess charge transfer from TiO2−x and subsequent reduction of MoDTC decomposition intermediates MoSxOy and/or MoSz, thereby preventing the MoO3 and/or FeMoO4 formation in MoDTC tribofilms. This finding may provide a new approach for improving the friction reduction performance of MoDTC-lubricated tribo-contacts.

Effects of annealing treatment on tribological behavior of tungsten-doped diamond-like carbon film under lubrication (Part 2): Tribological behavior under MoDTC lubrication

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.

Spectroscopy analyses of tribofilm and surface microcracks in carburized SCM420 steel under high-pressure rolling contact fatigue

The tribofilm and surface microcracks developed on a carburized SCM420 steel through a two-roller-type pitting test were characterized. A streaky 100- to 200-nm-thick tribofilm was generated on the specimen surface after 1.0 × 105 cycles. The tribofilm was identified to be mainly composed of calcium phosphate Ca3(PO4)2 and iron phosphate Fe3(PO4)2. Microcracks having lengths of a few tens of micrometers were detected on the contact surface without the tribofilm after the test. The number of cycles corresponded to a transition of the tangential force between two rollers decreasing to a stick-slip phenomenon as a steady state. A friction modifier additive (molybdenum dialkyldithiocarbamate) was added to a lubricant to improve rolling contact fatigue (RCF) pitting resistance. This lubricant containing the friction modifier additive exhibited a lifetime that was a factor of 10 greater than the RCF lifetime for the lubricant base oil. Therefore, the tribofilm may affect the tangential force and RCF lifetime. The contact surfaces and subsurface structure, especially in the vicinity of the microcracks, were dynamically reconstructed by severe friction and damage accumulation. Oxygen was detected on the surface of the microcracks.

Temperature dependence of molybdenum dialkyl dithiocarbamate (MoDTC) tribofilms via time-resolved Raman spectroscopy

Molybdenum dialkyl dithiocarbamate (MoDTC) is a friction reducing additive commonly used in lubricants. MoDTC works by forming a low-friction molybdenum disulphide (MoS2) film (tribofilm) on rubbed surfaces. MoDTC-induced MoS2 tribofilms have been studied extensively ex-situ; however, there is no consensus on the chemical mechanism of its formation process. By combining Raman spectroscopy with a tribometer, effects of temperature and shear stress on MoS2 tribofilm formation in steel-steel contacts were examined. Time-resolved Raman spectra of the tribofilm were acquired, together with the instantaneous friction coefficient. The tribofilm is constantly being formed and removed mechanically during rubbing. Increasing shear stress promotes MoS2 formation. The nature of the tribofilm is temperature-dependent, with high-temperature tribofilms giving a higher friction than lower temperature films. Below a critical temperature Tc, a small amount of MoS2 gives significant friction reduction. Above Tc, a patchy film with more MoS2, together with a substantial amount of amorphous carbon attributed to base oil degradation, forms. The composition of this tribofilm evolves during rubbing and a temporal correlation is found between carbon signal intensity and friction. Our results highlight the mechanochemical nature of tribofilm formation process and the role of oil degradation in the effectiveness of friction modifier MoDTC.

MoS2 tribofilm distribution from low viscosity lubricants and its effect on friction

The current study analyses the friction performance of low viscosity fully-formulated oils containing the Molybdenum Dialkyl Dithiocarbamate (MoDTC) friction modifier at different concentrations. The MoDTC friction modifier is known to produce MoS2 sheets in the tribocontact providing a low coefficient of friction under boundary lubrication conditions. However, there is a little knowledge around the quantitative relationship between the concentration of MoDTC in the oil and MoS2 amount and distribution in the contact. The study uses Raman spectroscopy mapping capability to characterise the tribofilm formed from different chemistry lubricants and under different tribological conditions as defined by the lambda ratio. After qualitative and quantitative chemical surface characterisation a discussion is presented to highlight some important aspects to relate the formed MoS2 sheets, their spatial distribution in tribofilms and the subsequent tribological performance.

Study Tribological Properties of MoDTC and Its Interactions With Metal Detergents

Abstract Recently, the synergistic tribological properties between molybdenum dialkyldithiocarbamate (MoDTC) and metal detergents have been the focus of significant attention due to the high requirements of engine oil. In this study, an SRV tribometer and four-ball machine were used to study the tribological performance of MoDTC combined with three types of metal detergents with different base numbers. Meanwhile, the detergency of the three metal detergents was also investigated using the hot tube test and crankcase simulation test. The results showed that (i) a high-based detergent possessed an excellent detergency performance compared with that of low-based detergents. (ii) The tribological properties of the base oil with a content of 0.75% MoDTC were superior to those of other contents at elevated temperatures. (iii) The metal detergents with a higher base number showed the best thermal stability, detergency performance, and anti-wear performance among the three types of metal detergents. The anti-wear mechanism was that the synergistic action of active elements in MoDTC and metal detergents promoted the generation of a tribological film.

Understanding the role of surface textures in improving the performance of boundary additives, part I: Experimental

Tribological performance of systems in boundary lubrication is dependent on contact and lubricant conditions such as temperature, lubricant additive concentration, surface characteristics, contact pressure and additive-additive interactions. Although past parametric studies have investigated these various factors, there are limited studies on the effect of surface topography on the performance of boundary lubrication additives. This is pertinent because of the increased use of surface texturing in lubricated contacts. This study has employed laser surface texturing to achieve surfaces with different topographies. The influence of the different surface topographies on the tribological performance of a friction modifier additive, molybdenum dialkyldithiocarbamate (MoDTC), was investigated. Results show that laser-textured surfaces in some instances can offer improved friction performance compared to non-textured (polished) surfaces when working positively with a friction modifier additive. Anisotropic surfaces resulted in improved friction. The mechanism for the improved performance of the laser-textured surfaces is believed to be through the augmented local contact pressures at the asperities that accelerate additive decomposition to form protective low-friction tribofilms. This study demonstrates the feasibility of surface texturing in improving the performance of boundary additives.

Effect of Organic-Mo on the Wear Behavior of Phenolic Resin Composites

Organic molybdenum (e.g., molybdenum dialkyldithiocarbamate, Mo-DTC) is a typical additive for liquid lubricants which can produce a significant anti-wear role with only a minor addition. In this article Mo-DTC additives were used to enhance the wear resistance of a phenolic resin. Phenolic/Mo-DTC composites with various Mo-DTC filler ratios were prepared by hot-press molding. The hardness and wear performance of the composites were measured by a Shore durometer and by an M-2000 friction and wear tester, respectively. The results showed that after adding the Mo-DTC filler, both the hardness and the anti-wear properties of the composites materials were improved. Under the condition of high-speed with a smooth ring, the wear scar length for the sample with 1% Mo-DTC content decreased by 45.6% compared with that of the neat phenolic resin whereas for a wire rope ring a decrease of 16% was observed for 0.5% Mo-DTC. Based on the wear morphology of the composites, the wear mechanisms of the designed phenolic/Mo-DTC composites were determined.

Comparative studies of the tribological behaviors and tribo-chemical mechanisms for AlMgB14-TiB2 coatings and B4C coatings lubricated with molybdenum dialkyl-dithiocarbamate

Abstract We compared the tribological behaviors and the tribo-chemical mechanisms of AlMgB14-TiB2 coatings and B4C coatings under lubrication with molybdenum dialkyl-dithiocarbamate (MoDTC). In unidirectional sliding contact, the boride coatings exhibited an unstable tribological performance, while the friction coefficients of these coatings maintained a very steady low level in reciprocating sliding contact. No severe wear occurred to the boride coatings. However, significant abrasive wear was observed on the steel balls rubbing against the boride coatings under unidirectional sliding contact. Analysis indicated incomplete dissociation of MoDTC at coating wear tracks and no formation of MoS2 tribofilms on steel counterfaces in the case of unidirectional sliding contact, whereas well-developed MoS2 tribofilms were formed on AlMgB14-TiB2 coatings under reciprocating sliding condition.

Ti content on the tribological properties of W/Ti-doped diamond-like carbon film lubricating with additives

In this study, tungsten and titanium co-doped diamond-like carbon films (W/Ti-DLC) on the AISI 316 L stainless steel substrate with different currents of Ti target are deposited by ion beam deposition/DC magnetron sputtering technology, and Ti contents in the W/Ti-DLC films varies from 0 to 1.9 at.%. The mechanical properties, chemical composition and tribological properties of the W/Ti-DLC films are analyzed by nano-indentation instrument, scanning electron microscopy (SEM), Raman spectrometer, X-ray photoelectron spectroscopy (XPS). The friction and wear behaviors of the films versus AISI 52100 steel ball under molybdenum dialkyldithiocarbamate (MoDTC) and zinc dialkyldithiophosphate (ZDDP) containing lubrication conditions are investigated by using an SRV tribometer. The results show that doping Ti with high content can cause graphitization on the film surface. The variances of the coefficients of friction and wear rates of the films with Ti content under lubrications are mainly governed by the graphitization and tribofilms formed on the worn surfaces. MoDTC presents better friction reduction effect on the W/Ti-DLC film and Ti content has effect on the formation of ZDDP derived tribofilm.

Influence of additives on the friction and wear reduction of oil-based drilling fluid

In comparison to conventional vertical hole drilling, extended reach drilling wells with long horizontal section require higher driving torque due to the increased drag on the drill string, drill column, casing and other equipment. This has led to higher friction and wear on the drilling equipment. Friction and wear preventive properties of oil-based drilling fluid is therefore important to keep oil extraction economical and sustainable. The addition of small concentrations of hydrocarbon additives to drilling fluid has shown significant positive effects on these properties. In this study, improvements in friction and wear properties of drilling fluid with the use of friction reduction additives was analyzed using a four-ball experimental configuration. Experiments resulted in wear in boundary and mixed lubrication regimes due to significant metal-metal interaction. The results showed that liquid friction reduction additives with long hydrocarbon tails and high metal affinity polar heads achieved better performance than additives that contained molybdenum dialkyldithiocarbamate. Energy dispersive spectroscopy results indicated lower levels of salts and corrosive chemicals on the surface of the wear scars for the best preforming additives.