Cooperative effect of surface alloying and laser texturing on tribological performance of lubricated surfaces

The cooperative effect of laser surface texturing(LST) and double glow plasma surface alloying on tribological performance of lubricated sliding contacts was investigated.A Nd:YAG laser was used to generate microdimples on steel surfaces. Dimples with the diameter of 150μm and the depth of 30-35μm distributed circumferentially on the disc surface.The alloying element Cr was sputtered to the laser texturing steel surface by double glow plasma technique.A deep diffusion layer with a thickness of 30μm and a high hardness of HV900 was formed in this alloy.Tribological experiments of three types of samples(smooth,texturing and texturing+alloying) were conducted with a ring-on-disc tribometer to simulate the face seal.It is found that,in comparison with smooth steel surfaces,the laser texturing samples significantly reduce the friction coefficient.Moreover,the lower wear rate of the sample treated with the two surface techniques is observed.

Novel water-based nanolubricant with superior tribological performance in hot steel rolling

Novel water-based nanolubricants using TiO2 nanoparticles(NPs)were synthesised by adding sodium dodecyl benzene sulfonate(SDBS)and glycerol,which exhibited excellent dispersion stability and wettability.The tribological performance of the synthesised nanolubricants was investigated using an Rtec ball-on-disk tribometer,and their application in hot steel rolling was evaluated on a 2-high Hille 100 experimental rolling mill,in comparison to those without SDBS.The water-based nanolubricant containing 4 wt%TiO2 and 0.4 wt%SDBS demonstrated superior tribological performance by decreasing coefficient of friction and ball wear up to 70.5%and 84.3%,respectively,compared to those of pure water.In addition to the lubrication effect,the suspensions also had significant effect on polishing of the work roll surface.The resultant surface improvement thus enabled the decrease in rolling force up to 8.3%under a workpiece reduction of 30%at a rolling temperature of 850◦C.The lubrication mechanisms were primarily ascribed to the formation of lubricating film and ball-bearing effect of the TiO2 NPs.

Preparation and Tribological Performance of Novel Organotin Compound as Lubricant Additive

Oil-soluble stannous naphthenate (SN) is synthesized by using naphthenatic acid and SnO. And its molecular structure is confirmed by IR and multielement oil analyzer (MOA). The tribological performances of the organotin as lubricant additive are evaluated with a four-ball friction and wear tester. These experiments indicate that the wear scar diameter (WSD) and friction coefficient are diminished while the load-carrying capability increased by comparison with that of base oil. The elemental composition of the boundary lubricating film is examined by means of Auger electron spectroscopy (AES). Synergistic effect is found in the load-carrying capability of the complex of SN and sulfured olefin. The analytical results of AES indicate that the good performance of stannous naphthenate is attributed to the formation of a boundary lubricating film containing Sn on the rubbed surface.

Effect of Cu addition on the microstructure and tribological performance of Ni60 directional structure coating

The Ni60/15wt% Cu directional structure coating was prepared by the composite technology of flame spraying, induction remelting,and forced cooling, and the effect of Cu on the microstructure, phase, hardness, and wear performance of Ni60 coatings was investigated. Results showed that Cu addition makes the microstructure of Ni60 directional structure coating more compact, and Cu is mainly enriched within the crystal grain, resulting in the formation of Cu_(3.8)Ni as the bonding phase. Compared with Ni60 directional structure coating, Ni60/Cu directional structure coating has a lower hardness, lower friction coefficient, and lower wear rate, which indicate that Cu can effectively enhance the antifriction performance of Ni60 directional structure coating.

Inorganic nanomaterial lubricant additives for base fluids,to improve tribological performance:Recent developments

In this paper,we review recent research developments regarding the tribological performances of a series of inorganic nano-additives in lubricating fluids.First,we examine several basic types of inorganic nanomaterials,including metallic nanoparticles,metal oxides,carbon nanomaterials,and"other"nanomaterials.More specifically,the metallic nanoparticles we examine include silver,copper,nickel,molybdenum,and tungsten nanoparticles;the metal oxides include CuO,ZnO,Fe_(3)O_(4),TiO_(2),ZrO,Al_(2)O_(3),and several double-metal oxides;the carbon nanomaterials include fullerene,carbon quantum dots,carbon nanotubes,graphene,graphene oxides,graphite,and diamond;and the"other"nanomaterials include metal sulfides,rare-earth compounds,layered double hydroxides,clay minerals,hexagonal boron nitride,black phosphorus,and nanocomposites.Second,we summarize the lubrication mechanisms of these nano-additives and identify the factors affecting their tribological performance.Finally,we briefly discuss the challenges faced by inorganic nanoparticles in lubrication applications and discuss future research directions.This review offers new perspectives to improve our understanding of inorganic nano-additives in tribology,as well as several new approaches to expand their practical applications.

Hydrothermal-assisted grinding route for WS_(2) quantum dots(QDs)from nanosheets with preferable tribological performance

The 2 D nanomaterials have achieved the superlubrication property whatever in solid or liquid lubrication in recent years.However,whether or not the nanosheets can stably disperse in oils and smoothly enter into the asperity of friction pairs is crucial for exerting the function of antifriction.The structure of 2 D QDs is desirable for addressing these issues due to its smaller 3 D size.In this study,we developed a facile preparation process for WS_(2) QDs with uniform 2 nm size from nanosheets via hydrothermal-assisted grinding approach.The structure of the as-obtained WS_(2) QDs was determined by a series of characterizations.The results showed that the as-obtained WS_(2) QDs exhibited the typical spectrum features of nanosized quantum dot.The results of the tribological performance in grease verified that the average friction coefficient(ACOFs) and wear volume(AWVs) were decreased by 7.89% and 63.90%relative to grease,respectively,exhibiting a preferable friction reducing and wear resistance.

Tribological Performance Improvement of Bearing Steel GCr15 by an Alternating Magnetic Treatment

This paper discusses the tribological performance of the bearing steel GCr15 treated by an alternating magnetic field. The wear test results showed that the average of wear mass losses decreased by nearly 80% after the magnetic treatment, compared to those before the magnetic treatment. The micro-hardness and microstructures（i.e., grain size,carbide morphology and dislocation distribution） before and after the magnetic treatment were experimentally investigated,and the mechanism of the tribological performance improvement of the bearing steel GCr15 due to the magnetic treatment was then revealed based on the above results.

Effective sugar-derived organic gelator for three different types of lubricant oils to improve tribological performance

In this study,the gelling ability and lubrication performance of N-octadecyl-D-gluconamides(NOG)in liquid paraffin(LP),pentaerythritol oleate(PE-OA),and polyethylene glycol(PEG)oils were systemically investigated.The NOG,which could gelate the investigated oils,was successfully synthesized by a one-step method.The prepared gel lubricants were completely thermoreversible and exhibited improved thermal stability,according to the thermogravimetry analysis(TGA)reports.Rheological tests confirmed that the NOG gelator could effectively regulate the rheological behavior of the base oils.Tribological evaluation suggested that NOG,as an additive in the three types of base oils,could remarkably reduce the friction and wear in steel contacts.A plausible mechanism for the improved performances was proposed based on the mechanical strength of the gels and the formation of the boundary-lubricating film on the worn surface.The results indicated that NOG is a potential gelator for preparing gel lubricants with excellent tribological properties and environment-friendly characteristics.

Tribological performance of various metal-doped carbon dots as water-based lubricant additives and their potential application as additives of poly(ethylene glycol)

Advances in nano-lubricant additives are vital to the pursuit of energy efficiency and sustainable development.Carbon dots(CDs)have been widely investigated in the domain of lubricant additives owing to their extraordinary tribological properties,in particular,their friction-reducing and anti-wear properties.Metal-doped CDs are a new type of CDs,and their friction-reducing and anti-wear properties are attracting increasing attention.Therefore,a series of CDs doped with various divalent metal ions have been successfully synthesized via one-pot pyrolysis.The tribological properties of the synthesized CDs as water-based lubricant additives are in the following order:Zn-CDs>Cu-CDs>>Mg-CDs>Fe-CDs>U-CDs.Specifically,adding 1.0 wt%of Zn-CDs into water-based lubricant results in 62.5%friction and 81.8%wear reduction.Meanwhile,the load-carrying capacity of the water-based lubricant increases from 120 N to at least 500 N.Zn-CDs as an additive have long service life.Additionally,anion-tuned Zn-CDs fabricated via anion exchange exhibit promise as lubricant additives for poly(ethylene glycol).Based on the results of wear scar surface analyses,it is discovered that tribochemical films,primarily composed of iron oxides,nitrides,metal carbonates,zinc oxides,zinc carbonates,organic compounds,and embedded carbon cores,formed on the rubbing surfaces with a thickness of approximately 270 nm when Zn-CDs are used as additives.This film combined with the“ball-bearing”and third-particle effects of Zn-CDs contributed to excellent lubrication performance.

Analysis and comparison of tribological performance of fatty acid-based lubricant additives with phosphorus and sulfur

Two environmentally friendly,water-based lubricant additives(phosphorus-containing ricinoleic acid(PRA)and sulfur-containing ricinoleic acid(SRA))were prepared.The lubrication perfor-mance of the additives in a water-based lubricant was tested using a four-ball tribotester.The stainless steel surface was analyzed by using scanning electron microscopy(SEM)and X-ray pho-toelectron spectroscopy(XPS).The additives reduced the coefficient of friction(COF)value,wear scar diameter(WSD)and improved the extreme pressure(PB)value.Water-based fluids con-taining the PRA exhibited lower COF,WSD,and PB values than the SRA.The good tribological performances of the PRA and SRA were attributed to the synergistic action of long aliphatic chains and highly active phosphorus and sulfur elements.

Optimizing the tribological performance of DLC-coated NBR rubber:The role of hydrogen in films

Diamond-like carbon(DLC)films directly deposited on rubber substrate is undoubtedly one optimal option to improve the tribological properties due to its ultralow friction,high-hardness as well as good chemical compatibility with rubber.Investigating the relationship between film structure and tribological performance is vital for protecting rubber.In this study it was demonstrated that the etching effect induced by hydrogen incorporation played positive roles in reducing surface roughness of DLC films.In addition,the water contact angle(CA)of DLC-coated nitrile butadiene rubber(NBR)was sensitive to the surface energy and sp?carbon clustering of DLC films.Most importantly,the optimum tribological performance was obtained at the 29 at%H-containing DLC film coated on NBR,which mainly depended on the following key factors:(1)the DLC film with appropriate roughness matched the counterpart surface;(2)the contact area and surface energy controlled interface adhesive force;(3)the microstructure of DLC films impacted load-bearing capacity;and(4)the generation of graphitic phase acted as a solid lubricant.This understanding may draw inspiration for the fabrication of DLC films on rubber to achieve low friction coefficient.

Effect of electrolyte concentration o n the tribological performance of MAO coatings on aluminum alloys

Micro-arc oxidation(MAO)is an efficient approach to improve the hardness,wea r resistance,and other properties of aluminum alloys.In order to investigate the effect of the electrolyte concentration on the properties of MAO coatings for LY12 alloy,the voltage variation during the MAO process was recorded.The surface morphologies and phase compositions of the coatings produced with different electrolytes were investigated using scanning electron microscopy and X-ray diffraction,respectively.The roughness and thickness of the coatings were measured using a pocket roughness meter a nd an eddy-current thickness meter,respectively.The tribological performances of the coatings wer e investigated against GCr15 bearing steel on aball-on-disc wear tester in open air.The results showed that with an increase in the Na2SiO3 content,the working voltage of the MAO process decreased,the roughness a nd thickness of the coatings increased significantly,a nd the relative content of the α-Al2O3 phase decreased.With an increase in the KOH content,the working voltage decreased slightly,the roughness and thickness of the coatings increased slightly,and the α-and γ-Al2O3 phase contents remained unchanged.The friction coefficient and wear rate of the coatings increased with an increase in the Na2Sio3 and KoH concentrations.A decrease in the porosity and roughness and an increase in the α-Al2O3 content of the coatings reduced their wear mass loss.

Effects of Additives on the Microstructure and Tribology Performance of Ta-12W Alloy Micro-Arc Oxidation Coating

Oxide ceramic coatings were fabricated on tantalum alloys by micro-arc oxidation (MAO) to improve their hardness and tribological properties. The MAO coatings were manufactured in a mixed silicatephosphate electrolyte containing NaF and/or EDTA (ethylene diamine tetraacetic acid). The surface morphology,cross-sectional view, chemical composition, hardness, and wear performance of the coatings were analysed. As revealed by the scanning electron microscopy, silica-rich nodules appear on the MAO coating obtained in the silicate-phosphate electrolyte, but the formation of nodules is inhibited with NaF and/or EDTA in the electrolyte.Also, they reduce the roughness and improve the compactness of the coatings, which are composed of Ta_(2)O_(5),(Ta, O), and TaO. A thick and hard coating is obtained in the NaF-containing electrolyte, and the tribology performance is effectively improved. With additives, the nodule structure is detached from the coating surface and dissolved in the electrolyte. By using NaF as an electrolyte additive, the abrasion performance of the MAO coating is enhanced by decreasing the nodule structure, increasing the size of micropores, and improving the coating hardness.

Influence of Ag content on the microstructure, mechanical, and tribological properties of TaVN–Ag films

A series of TaVN-Ag nanocomposite films were deposited using a radio-frequency magnetron sputtering system. The micro- structure, mechanical properties, and tribological performance of the films were investigated. The results showed that TaVN-Ag films were composed of face-centered cubic （fcc） TaVN and fcc-Ag. With increasing Ag content, the hardness of TaVN-Ag composite films first in- creased and then decreased rapidly. The maximum hardness value was 31.4 GPa. At room temperature, the coefficient of friction （COF） of TaVN-Ag films decreased from 0.76 to 0.60 with increasing Ag content from 0 to 7.93at%. For the TaVN-Ag films with 7.93at% Ag, COF first increased and then decreased rapidly from 0.60 at 25℃ to 0.35 at 600℃, whereas the wear rate of the film increased continuously from 3.91 × 10^-7 to 19.1 × 10^7 mm3/（N·mm）. The COF of the TaVN-Ag film with 7.93at% Ag was lower than that of the TaVN film, and their wear rates showed opposite trends with increasing temperature.

Tribological Properties of Dimpled Surface Alloying Layer on Carbon Steel

The effect of surface structure and coating on tribological properties of 45^# carbon steel disc was analyzed. A Nd：YAG laser was used to generate rnicrodirnples on steel surfaces. Dimples with diameter of 150 rn and depth of 50 rn were distributed in an orbicular array on disc surface. Then the alloying element Mo was sputtered to 45# carbon steel disc surface by means of double glow plasma technology. Diffusion Mo alloying layer with 30min thickness and high hardness up to 0.025 was formed on the disc surface. Tribological experiments of three types samples （smooth, texturing and texturing＋alloying） were conducted with a pin-on-disc tribometer. It is found that the dimpled-samples are most effective for reducing friction in comparison with smooth steel surthces, improving the lubricating state from boundary to hydrodynamic region.

Tribological Behavior of Plant Oil-Based Extreme Pressure Lubricant Additive in Water-Ethylene Glycol Liquid

A water-soluble lubricant additive(RSOPE)was prepared by esterification reaction using fatty acid from rubber seed oil.The RSOPE was added into water-ethylene glycol(W-EG)solution as lubricant additive.Dispersion stability and rheological properties were investigated.We used a four-ball tribotester to assess the lubrication performance of W-EG based fluid with the RSOPE additive.The stainless-steel surface was analyzed using scanning electron microscopy(SEM)and X-ray photoelectron spectroscopy(XPS).Good dispersion stability was observed in the RSOPE/W-EG solutions.Furthermore,non-Newtonian fluid behavior at low shear rates and Newtonian fluid behavior at high shear rates was exhibited.The addition of RSOPE into water-glycol reduced the friction coefficients(COF)and wear scar diameters(WSD).The maximum non-seizure loads(PB)increased from 98 N to 752 N and the W-EG solution with RSOPE had good corrosion resistance properties.Good tribological performances for W-EG solution with RSOPE were attributed to the boundary tribofilm composed of iron oxide,iron phosphide and so on.

Tribological Behaviors of S,B-Containing Morpholine Derivatives as Additives in Rapeseed Oil

Two novel ashless and non-phosphorus S, B-containing morpholine derivatives, MBOC and MBOD, were prepared and their tribological behaviors in rapeseed oil （RSO） were evaluated using a four-ball tester. Thermal degradation tests were conducted to identify their thermal stabilities using a thermo-gravimetric analyzer. The worn surfaces of the steel balls were investigated by scanning electron microscopy （SEM）. The results indicated that the additives possessed high thermal stabilities and good load-carrying capacities. Moreover, they both had good anti-wear and friction reducing property at a relatively high concentration （1.5 m%） and under all test loads. The results of XPS analyses illustrated that the prepared compounds as additives in RSO could form a protective film containing inorganic sulfide, sulfate, oxidized compounds and organic nitrogen-containing compounds on the metal surface during the sliding process.

Numerical investigation of microtexturing rings＇ structure on the friction performance of bearing cells

We presented a numerical examination of the effect of microtexturing negative rings' structure on the tribological performance of parallel bearing couples' cell. Three mcirotexturing rings, which are circle, square and ellipse, were chosen and the analysis model were established. We used the Reynolds equation coupled with finite difference method and successive over relaxation Gauss-Seidel iterative method to solve the Newtonian flow's hydrodynamics within a bearing couple. The effect of texture density and radius ratio(thickness) of the microtexturing rings were investigated on the tribological performance under the similar operating conditions. The numerical simulation reveals that: 1) The microtexturing rings' structure can homogenize the local pressure much uniformly within the bearing cell. 2) The tribological performance is determined mainly by the microtexturing rings' geometry and texture density, and the thickness of the rings' structure can help to change the quantitative values. 3) The square and circle rings' s microtexturing surface can slightly improve the frictional performance with the bearing cells' gap, while the ellipse ring's surface may decrease the frictional performance. 4) The ellipse rings' microtexturing surface can achieve the minimum spacing gap but the maximum friction coefficient of the bearing couple, and then the circle and square rings' structure take the second and third place, respectively.

Tribological study of two ammonium chloride-decanoic acid deep eutectic solvents(DESs)as high-performance lubricants

Deep eutectic solvents(DESs)are acknowledged as a novel class of functional liquid.DESs share similar physical properties with ionic liquids(ILs)and have the potential to be a novel class of lubricants.In this study,two DESs,namely tetrabutylammonium chloride-decanoic acid DES(C4-DES)and methyl tricaprylmethylammonium chloride-decanoic acid DES(C8-DES),were synthesized,and their physico-chemical properties and tribological performances were evaluated.Post-analysis of the rubbing surfaces used multiple techniques to gain insights into the lubrication mechanisms.Results show that the coefficient of friction(COF)and wear were reduced by approximately 29%and 91%for the C4-DES,and 36%and 94%for the C8-DES,compared to an ester base oil.The friction reduction behavior of the DESs is attributed to the monolayer adsorption of the polar group in the decanoic acid(DEAC),whose effectiveness is affected by the component of the ammonium salts in the DESs and the operating temperatures.In addition to the adsorbed film,worn surface analysis revealed that an ultra-thin tribochemical film with a thickness of 3–7 nm was formed on the surfaces lubricated with the C8-DES.The composition of the film was studied,and the lubrication mechanisms of the two DESs were discussed.

Influence of Ti target current on microstructure and properties of Ti-doped graphite-like carbon films

Ti-doped graphite-like carbon （Ti-GLC） films were synthesized successfully by magnetron sputtering technique. The compositions, microstructures and properties of the Ti-doped GLC films dependent on the parameter of Ti target current were systemically investigated by Raman spectra, X-ray photoelectron spectroscopy （XPS）, X-ray diffraction （XRD）, scanning electron microscopy （SEM）, atomic force microscopy （AFM）, nanoindentation and ball-on-disk tribometer. With the increase of the Ti target current, the ratio of sp2 bond and the content of Ti as well as the film hardness and compressive internal stress increase, but the high content of the Ti would result in the loose film due to the formation of the squamose structure. Less incorporated Ti reduces the friction of the GLC film in dry-sliding condition, while pure GLC film exhibits the lowest friction coefficient in water-lubricated condition. Ti-GLC film deposited with low Ti target current shows high wear resistance in both dry-sliding and water-lubricated conditions.