Molybdenum Dialkyldithiophosphate Research Articles

Sandwich-like tribofilm induced highly effective lubrication for MoDTP coupled with hydroxy-magnesium silicate (MSH)

In the field of lubrication enhancement, nanomaterials are becoming increasingly important. However, the issue of their stable dispersion in lubrication oil remains a persistent challenge. To address this issue, we synthesized two distinct morphologies of MSH nanomaterials, subsequently modifying them with alkylsilane (OTMS) to enhance their dispersion stability. Particularly, the 1.0 wt% of OTMS-modified laminar MSH (LMSH@OTMS) combined with 0.3 wt% molybdenum dialkyldithiophosphate (MoDTP) exhibited remarkable lubricating performance in PAO10. The result indicate there is a synergistic effect between two components, resulting in the formation of a main sandwich-like tribofilm. The tribofilm is comprised of two distinct layers: a lubricating layer derived from MoDTP and an anti-wear layer stemming from LMSH@OTMS. These findings offer significant potential for enhancing durability of mechanical systems.

Study on anti-wear and friction-reducing compounding additives in lithium greases

PurposeThis paper aims to determine a suitable anti-wear and friction-reducing compounding additive for lithium greases (LG) by investigating the effects of three single additives potassium borate (PB), zinc dialkyl dithiophosphate and molybdenum dialkyl dithiophosphate (MoDDP) and two compound additives on the friction, wear and extreme pressure properties of LG.Design/methodology/approachThe effects of the above five additives on the friction, wear and extreme pressure properties of LG were investigated using an SRV-5 friction tester. An X-ray photoelectron spectrometer was used to analyze the various elements presented on the wear surface as well as the types of compounds.FindingsThe compound additive suitable for grease consists of PB and MoDDP, which have excellent friction reduction, anti-wear and extreme pressure properties. And a boundary protection film consisting of oxide and MoS2 is formed on the friction surface, thus improving the friction reduction and anti-wear performance of the grease.Originality/valueThis study can improve the anti-wear and friction-reduction performance of greases, which is of great importance in the field of industrial lubrication. The results of this paper are expected to be useful to researchers and academics of grease.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-11-2022-0350/

Rheological and tribological properties of polyurea greases containing additives of MoDDP and PB

Molybdenum dialkyl dithiophosphate (MoDDP) and potassium borate (PB) were selected as additives for the greases. Results show that the polar MoDDP additive cause grease colloidal stability enhanced and apparent viscosity and structural strength increased, while potassium borate has less effect on the colloidal structure and structural strength of the grease. The solid additive PB has excellent anti-wear, extreme pressure and friction reduction properties at room temperature as well as at high temperatures under low loading conditions. Due to the synergistic effect, the PB/MoDDP additive combination can achieve excellent friction reduction and anti-wear performance. Under high temperatures, the content of metal phosphates and molybdenum disulfide decreases, the adsorption capacity of additives decreases, and friction and wear on metal surfaces increase.

Hydro-liquefaction of asphaltene catalyzed by molybdenum-nickel bimetallic catalysts in slurry bed

Abstract The aim of this study is to achieve the hydro-liquefaction of asphaltene for the production of liquid fuel. The oil soluble molybdenum catalysts, molybdenum dialkyl dithiophosphate, and nickel carboxylate precursor with different carbon chains, were synthesized. The catalysts were characterized by ICP-OES, TEM and XPS. Their catalytic performance for the hydro-liquefaction of asphaltene to liquid fuels was investigated in a slurry bed reactor by using decalin as hydrogen donor and dispersant. The results show that the bimetal catalytic system composed of molybdenum dialkyl dithiophosphate and caproic acid nickel produces more MoS2 and NiS x active species. The metal contents of which accounts for 81.8 and 81.0 wt% of the total amount of Mo and Ni, respectively, and thus exhibits the best catalytic performance among the catalysts studied. The liquid yield of the asphaltene hydrogenation over the bimetal catalyst is 84.6 wt%, which is much higher than that over other catalysts, and the coke content is only 8.6 wt% under the conditions of 1000 μg/g of total metal addition, 1:1 Mo/Ni metal mass ratio and 1:1 asphaltene/naphthalene mass ratio. The content of saturated and aromatic components in the liquid products of asphaltene hydrogenation of the bimetal catalyst system is 78.9 wt%, which is a high-quality liquid fuel component.

Formation mechanisms of zinc, molybdenum, sulfur and phosphorus containing reaction layers on a diamond‐like carbon (DLC) coating

AbstractDiamond‐like carbon (DLC) coatings are nowadays successfully applied on industrial components like pistons, piston rings and bearings in lubricated tribological contacts due to friction and wear reducing effects. In contradiction thereto, todays lubricants and additives are designed for tribological steel/steel contacts, whereby the knowledge on tribochemical layer formation on steel surfaces is comprehensive in contrast to the physical‐chemical interactions between diamond‐like carbon coatings, lubricants and additives. Therefore the formation mechanisms of zinc, molybdenum, sulfur and phosphorus containing reaction layers on a zirconium modified diamond‐like carbon coating a‐C : H : Zr (ZrCg) in lubricated tribological contacts were analyzed by means of pin‐on‐disc (PoD) tribometer by varying the distances from s = 200 m–3,000 m under boundary and mixed friction conditions at T = 90 °C and a contact pressure p = 1,300 MPa regarding the application of diamond‐like carbon coatings on gears. The base lubricant poly‐alpha‐olefin (PAO) was formulated using the anti‐wear (AW) and extreme pressure (EP) additive zinc dialkyldithiophosphate (ZnDTP) and the friction modifier (FM) additive molybdenum dialkyldithiophosphate (MoDTP). The chemical composition of the tribochemical reaction layers by means of and Raman spectroscopy and x‐ray photoelectron spectroscopy (XPS) as well as for the thickness differ significantly by varying the additivation.

Formation of tribochemical reaction layers on a metal modified amorphous carbon coating a-C:H:Zr (ZrCg)

Abstract The aim of this paper is to analyze the formation of tribochemical reaction layers on a metal and hydrogen containing diamond-like carbon (DLC) coating in tribological contacts using a molybdenum dialkyl dithiophosphate (MoDTP-) and zinc dialkyl dithiophosphate (ZnDTP-) formulated lubricant. Therefore the industrially relevant gear oil polyalkylene glycol (PAG) as well as the additives MoDTP, ZnDTP and anglamol 99, containing Sulphur and Phosphorus (S-P), were used as lubricant in pin-on-disc (PoD) tribometer tests. The study was conducted using the DLC coating a-C:H:Zr (ZrCg). Chemical analyses on the wear tracks of the DLC coated specimens prove the formation of tribochemical reaction layers.

Molybdenum Dialkyldithiophosphate as self-sulfurized catalyst precursor in Hydrocracking of Residue

The molybdenum dialkyldithiophosphate (MoDTP) with the feature of self-sulfurization, has been prepared, characterized and evaluated in the slurry-phase hydrocracking of Karamay atmospheric residue (KAR) as catalyst precursor. The self-sulfurization of MoDTP achieved fine MoS2 particles with lower crystallinity and higher surface Mo4+ proportion in contrast to that of molybdenum naphthenate, implying the well sulfurized statement of MoDTP. Low coke yield and large asphaltene aggregate size using MoDTP proved the favorable hydrogenation activity of self-sulfurized catalyst in hydrocracking of residue.

The Synergetic Effects of Surface Texturing and MoDDP Additive Applied to Ball-on-Disk Friction Subject to Both Flooded and Starved Lubrication Conditions

This paper reports a novel work on the synergetic effects of microscale surface texturing and lubricant friction modifier additive of molybdenum dialkyldithiophosphate (MoDDP) subject to both flooded and starved lubrication conditions. The experiments were performed on reciprocating ball-on-disk friction in GTL8 base oil with and without MoDDP. In the flooded lubrication condition, the test results demonstrated that the presence of the MoDDP additive contributed to lower friction coefficients and also more pronounced effect of surface textures on friction than in the case of the bare base oil. In the starved lubrication experiments, textured and texture-free surfaces in the oils with and without MoDDP additive were tested until an abrupt rising of friction coefficient was detected. The results showed that the magnitude of friction coefficient before terminating each test was the almost same for various tests, while the endurance time in different test conditions was significantly different. The textured surface exhibited longer endurance time than the texture-free surface, especially when the MoDDP additive was used. The mechanism of the synergetic effects of surface textures and MoDDP additive has been discussed based on the experimental observations in the following sections. This study provides a new idea for the application of surface texture in boundary lubrication when lubricant additive is contained in the lubricating oils.

Effects of lubricants on the rolling performances of cold rolled copper strips

Two parameters in rolling process, the forward slip value (Sh) and the minimum rolling gauge (hmin) were tested using a 4-high rolling mill in order to investigate the rolling performances of cold rolled copper strips under different lubricating conditions viz, lubrication with (i) base oil, (ii) base oil with 0.5wt.% oiliness, (iii) base oil with 0.5wt.% dialkyldithiophosphateester(DDE) and (iv) base oil with 0.25wt.% DDE and 0.25wt.% molybdenum dialkyldithiophosphate (MoDDP). The surface roughness of rolled copper strips was measured by a laser scanning confocal microscope. The surface morphologies of copper strips were observed by a scanning electron microscopy (SEM) and the compositions of the surface residues were analyzed with an energy dispersive spectrometer (EDS). Results showed friction coefficients, which were calculated by Sh with different lubricants ranged from 0.067-0.302. The surface topography of copper strips showed smooth and the plowing wear was finer. Meanwhile, when the lubricant was base oil with 0.25wt.% DDE and 0.25wt.% MoDDP, the hmin of copper reached 19μm, a value satisfied the copper foil conduction. However, with the addition of EP additives, the topographies showed some grind pits at local region. Indicating that EP additives containing P, S, Mo moieties possess a better thickness-reducing performance, but cause corrosion at the same time.

Tribological properties of polyalphaolefin oil modified with nanocarbon additives

Enhancing the tribological properties and performance of lubricants with nanoparticle additives is an active area of research. Results of block-on-ring experiments examining tribological properties of polyalphaolefin (PAO) oil containing small amount of nanocarbon additives are reported in this study. Comparative analysis of coefficient of friction (COF) and wear was performed for PAO oil containing nanodiamond particles, onion-like carbon (OLC), single/multiwall carbon nanotubes (SWNT/MWNT) or nanographene platelets (NGPs). The performance of PAO oil samples containing nanodiamond additives was considerably different from those containing sp2 nanocarbon additives. The presence of sp2 nanocarbons reduced the COF of PAO by ~8–12 times. This effect on the COF was accompanied by a reduction in wear with the addition of carbon nanotubes and NGP; however, the wear was slightly increased in the presence of OLC. The presence of nanodiamond reduced the COF by ~70×, and the wear was significantly increased. The performance of nanocarbon particles in PAO in combination with molybdenum dialkyldithiophosphate (MoDDP) was also investigated. The combination of polishing capability of nanodiamonds with the protective action of MoDDP resulted in the reduction of both wear and COF as compared to pure PAO. In contrast, the combination of sp2 nanocarbons with MoDDP caused degradation of the PAO lubrication performance.

Nanodiamond-Based Nanolubricants: Investigation of Friction Surfaces

Synergistic compositions of detonation nanodiamond (DND) particles with polytetrafluoroethylene and molybdenum dialkyldithiophosphate were used in ring-on-ring, four-ball, and block-on-ring tests as an additive to polyalphaolefins and engine oils. Modest to significant reductions in the friction coefficients, wear, or both were observed. In the wear scars produced in the block-on-ring tests, the friction surfaces were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and profilometry. Significant polishing effects of the friction surfaces in lubricants containing DND were revealed in SEM observations and roughness measurements. The roughness of the scar surfaces produced in the presence of DND additives was about 35% lower than the roughness of the scars observed in pure oil experiments.

Tribological Properties of Motor Oil with Nanodiamond Additive tested for steel friction surfaces with different hardnesses – ERRATUM

Synergistic compositions of detonation nanodiamond (ND) particles in the form of 100nm aggregates in combination with molybdenum dialkyldithiophosphate were used as additives to 10W40 oils. Ring-on-disk tribological tests were performed under high load conditions using friction pairs with different hardnesses, namely normalized-normalized (“soft/soft”) and normalized-quenched (“soft/hard”) steel samples. For the “soft/hard” steel friction pair NDs provide significant reduction in both the coefficient of friction and wear as well as demonstrate polishing. For the “soft/soft” steel friction pair, however, no difference in the coefficients of friction was observed when the base oil was used with or without ND. In the test with oil containing the ND additive, the wear scar in the disk was wider, but more shallow, than in the test with pure oil. Current tests indicate that the significance of the reduction of friction and wear of the sliding surfaces in the presence of the ND additive in oil strongly depends on the hardness of the friction surfaces and most probably is connected with ND polishing effect.

Tribological Properties of Motor Oil with Nanodiamond Additive tested for steel friction surfaces with different hardnesses

ABSTRACTSynergistic compositions of detonation nanodiamond (ND) particles in the form of 100nm aggregates in combination with molybdenum dialkyldithiophosphate were used as additives to 10W40 oils. Ring-on-disk tribological tests were performed under high load conditions using friction pairs with different hardnesses, namely normalized-normalized (“soft/soft”) and normalized-quenched (“soft/hard”) steel samples. For the “soft/hard” steel friction pair NDs provide significant reduction in both the coefficient of friction and wear as well as demonstrate polishing. For the “soft/soft” steel friction pair, however, no difference in the coefficients of friction was observed when the base oil was used with or without ND. In the test with oil containing the ND additive, the wear scar in the disk was wider, but more shallow, than in the test with pure oil. Current tests indicate that the significance of the reduction of friction and wear of the sliding surfaces in the presence of the ND additive in oil strongly depends on the hardness of the friction surfaces and most probably is connected with ND polishing effect.

Anti‐wear performance of organomolybdenum compounds as lubricant additives

AbstractA four‐ball tester was used to evaluate the anti‐wear performance of three kinds of organomolybdemun compounds in engine oils and lithium soap grease, i.e. molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate (MoDTC), and sulphur‐ and phosphorus‐free organomolybdeum (molybdate). The results indicate that a low concentration of MoDDP does not improve the anti‐wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti‐wear properties of the engine oils. MoDTC does not improve the anti‐wear properties of the engine oils, but worsens the anti‐wear properties of the oils. Significant improvement of the anti‐wear properties is obtained with molybdate added in the four fully formulated oils. Both MoDDP and molybdate have good anti‐wear properties in the lithium soap grease, especially MoDDP with a high concentration. Copyright © 2006 John Wiley & Sons, Ltd.

Study on tribological and corrosion inhibiting properties of thiadiazole derivative as lubricant grease additive

PurposePure 2,5‐dimercapto‐1,3,4‐thiadiazole (DMTD) disulfide dimer (DMS2) shows excellent four ball weld properties, however, the product is a solid material with relatively low initial seizure load and exhibits certain corrosion, which accelerate oxidation of the lubricant by catalytic effect on metals. The author make efforts to resolve problems said by design a novel thiadiazole complex.Design/methodology/approachThe complex of thiadiazole dimmer and polyglycol (DMS2‐GL) was synthesized as ashless grease additive. The antiwear and load carrying properties of the additive and their synergistic effects was evaluated by four ball tester in four types of lubricant grease. Moreover, corrosion inhibiting properties of compositions said was investigated by copper corrosion test.FindingsThe additive DMS2‐GL possessed good load carrying capacity, and exhibits good synergistic antiwear and load carrying prop with rust inhibitor. In addition, dates obtained from copper corrosion test show that it does not corrode copper but coats the metal with a film, and could improve the anticorrosion of corrosive additives molybdenum dialkyldithiophosphate (MoDDP) and molybdenum dibutyldithiocarbamate (MoDTC) by forming protective films on rubbing surface, which contribute to improving corrosion inhibiting property of greases. Finally, the tribo‐chemical mechanism was proposed that thiadiazole dimer and polyglycol could coordinate with each other by polydentate surface interaction, which means thiadiazole rings interact with the metal surface, polyglycol affords a bridging technology linked thiadiazole dimmers so as to lighten loads and strengthen forces between thiadiazole dimmer moleculars.Originality/valueThis paper provides a good ashless additive which has good antiwear, extreme pressure and corrosion inhibiting properties, and fulfils an identified resources need, which can offer practical help in industrial applications and to an individual starting out on an academic career.

Antiwear synergism between organomolybdenum compounds and a ZnDDP

A four-ball machine was used to evaluate the antiwear performance of three kinds of organomolybdenum compounds — molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate (MoDTC), and sulphur- and phosphorus-free organomolybdenum — and their antiwear synergistic effect with a zinc dialkyldithiophosphate (ZnDDP). The results indicate that the three organomolybdenum compounds have good antiwear properties, especially MoDDP, and the organomolybdenum compound — especially MoDTC and sulphur- and phosphorus-free organomolybdenum compound — exhibit good antiwear synergisms with ZnDDP in a paraffin base oil. Copyright © 2006 John Wiley & Sons, Ltd.

Nondestructive characterization of surface chemical wear films via X-rays

This work describes and demonstrates a suite of techniques for the non-destructive examination of surface films formed from oil additives. X-Ray diffraction, reflectivity and fluorescence have been used in grazing-incidence geometry to provide information on the thickness, roughness, density, structure and composition of the layers that compose reaction films. The lubricating oils were not rinsed off the surfaces of the samples before analysis. Films were formed from neat polyalphaolefin (PAO) oil and PAO with chloroform, dimethyl disulfide, or zinc or molybdenum dialkyl dithiophosphate additive. A thick layer of crystalline FeO formed during wear lubricated by neat PAO.

Nondestructive characterization of surface chemical wear films via X-rays

This work describes and demonstrates a suite of techniques for the non-destructive examination of surface films formed from oil additives. X-Ray diffraction, reflectivity and fluorescence have been used in grazing-incidence geometry to provide information on the thickness, roughness, density, structure and composition of the layers that compose reaction films. The lubricating oils were not rinsed off the surfaces of the samples before analysis. Films were formed from neat polyalphaolefin (PAO) oil and PAO with chloroform, dimethyl disulfide, or zinc or molybdenum dialkyl dithiophosphate additive. A thick layer of crystalline FeO formed during wear lubricated by neat PAO.

Comparison of boundary lubrication films formed under four‐ball friction test conditions with different AW/EP Additives‐an X‐ray photoelectron spectroscopy study

AbstractThe antiwear and extreme‐pressure properties of six different types of additive (molybdenum dialkyldithiophosphate, dibenzyl disulphide, molybdenum dialkyldithiocarbamate, zinc dialkyldithiophosphate, chlorinated paraffin wax, and triaryl phosphate) were evaluated by standard four‐ball friction and wear tests. This was followed by scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS), and X‐ray photoelectron imaging (XPI) analyses of the worn surfaces to determine the structure of the boundary lubrication film and the mechanism of the tribochemical reaction occurring during the friction process. The presence of the additives in the base oil significantly increased the weld load and drastically reduced the wear‐scar diameter, suggesting antiwear and extreme‐pressure properties of the additives. The enhanced antiwear and loadcarrying capacity of the additive‐containing oils was attributed to the formation of a complex boundary lubrication film formed between the surfaces during the friction process as a result of the tribochemical reaction. The antiwear and extreme‐pressure properties of the additives were explained based on the XPS data. The studies indicated that the lubricating properties of the additives depend on their chemical nature and reactivity with metal surfaces.

Additive–additive interaction: an XPS study of the effect of ZDDP on the AW/EP characteristics of molybdenum based additives

The effect of zinc dialkyldithiophosphate (ZDDP) addition on the antiwear (AW) and extreme pressure (EP) properties of molybdenum dialkyldithiocarbamate (MoDTC) and molybdenum dialkyl dithiophosphate (MoDTP) are evaluated by standard Four-Ball friction test and also by the determination of coefficient of friction using an oscillating SRV apparatus. The boundary lubrication film formed on the worn surface using the two molybdenum additives and their combination with ZDDP is investigated by depth profile X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) to find out the chemistry of tribochemical reaction occurring at the surface during friction. It is seen that MoDTP possesses better AW properties than MoDTC due to its high reactivity with the metal surface. Nevertheless, the AW characteristics of MoDTC could be improved by the addition of ZDDP. The frictional properties of MoDTP, however, do not change by the addition of ZDDP. The synergistic action of ZDDP on MoDTC is attributed to the enhanced decomposition of MoDTC in presence of ZDDP. This is tentatively explained in terms of some interaction of zinc with the electron donating nitrogen present in MoDTC, which would have helped to increase its tribo-reactivity. XPS studies revealed that in the presence of ZDDP, MoDTC form mainly metal sulphides like MoS 2 and FeS under friction. The MoDTP+ZDDP derived surface, on the other hand, produced mainly metal phosphate along with molybdenum oxysulphides and small amount of MoS 2 and FeS. The mechanism of action of additives is explained.