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.

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.

Effect of hot rolling on microstructure and tribology behaviors of Ti-50.8Ni alloy

We link different microstructures to tribological behaviors of Ti-50.8 Ni(mole fraction, %) in reciprocating mode at room temperature(20 ℃). Hot-rolled alloys with B2 phase exhibit lower coefficient of friction and wear rate compared to the ones with B19?. Stress-induced martensitic transformation occurs during sliding. However, multi-pass hot rolling weakens the wear resistance. In this study, microstructures were characterized through electron backscatter diffraction and transmission electron microscopy(EBSD/TEM). From the concept of energy conservation, the effects of weak intensity of hot-rolled textures on the wear resistance are minimal. Based on the result that the alloy with a higher portion of coincidence site lattice boundaries shows lower martensitic start transformation temperature in the DSC curves than that with higher KAM values, the delay on B2-B19? transformation from {112}B2 twins outweighs dislocations. Moreover, widely distributed small-angle grain boundaries owing to dynamic recovery improve the wear resistance effectively compared to those that are well-recrystallized.

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.

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.

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.

Sensitivity and Compatibility Analysis of Sulfur and Phosphorus Type Additives in Rapeseed Oil

The effects of sulfur type additives T321 and phosphorous type additives P120 on the EP and AW abilities of rapeseed oil were investigated by a four-ball testing machine using the rapeseed oil as base oil.The effect of T321 mixed with P120 on the tribochemical performance of the rapeseed oil was studied.The result shows that the load carrying,extreme pressure and abrasion capacities of lubricant film can be improved by adding T321 and P120 as additives in rapeseed oil, respectively. The SEDX analysis on the surface of steel balls reveals that tribochemical reactions occur during the friction process, the barrier lubricating film is formed containing triglyceride and the additives can improve the anti-wear ability and load-carrying capacity.

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.

Design of wear-out-failure in-situ repair parts by environment-friendly nanocopper additive

Oleic acid surface-modified Cu nanoparticles with an average size of 20 nm were prepared by liquid phase reducing reaction. The tribological performance and mechanism of nanocopper as additive were studied by means of tribotester, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and nanoindentation instrument. The results indicate that the modified nanocopper additive can significantly improve the wear resistance and reduce friction coefficient of base oil. A copper protective film is formed and contributes to the excellent tribological properties of nanocopper additive. On the basis of the film forming mechanism, a new in-situ repair method was designed and used to repair wear-out-failure injection pump plunger and barrel. Furthermore, the current research progress of nanoparticles as green energy-saving lubricating oil additives were presented.

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.

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.

Tribology behaviors of Ti-Ni51.5 at% shape memory alloy with different microstructures and textures

The microstructure characteristics of TiNi alloy were investigated to elucidate the active deformation mechanisms during hot rolling and the corresponding tribology performance.The deformation was mainly dominated by a combination of mechanical twinning involving the {114}_(B2) and {112}_(B2) twins,dislocations,and stacking faults during the manufacturing process.Moreover,various heat treatments were performed to differentiate the discrepancies in tribological behaviors of hot-rolled and heattreated alloys.Hot-rolled microstructures with high defect density approximate to nanoscale precipitates through aging as the wear resistance of the alloy improves,albeit it is softer compared to the aged one.As demonstrated by the X-ray diffraction(XRD) results of the wear tracks,microstructures undergo the stress-induced martensitic(SIM) transformation during dry sliding.From differential scanning calorimetry(DSC) analysis,the martensitic transformation temperature is lowered by defects in the austenite phase.The activation of the SIM transformation can be a sluggish process owing to the effect of twinning,where both primary and secondary twins are involved.Furthermore,a reversible transformation that is related to pseudoelasticity causes a decrease in wear volume at room temperature,which is higher than the austenite finish temperature.Meanwhile,abrasive wear advances toward adhesion.Additionally,the hot-rolled sheet with y fiber-{111}//ND(normal direction) exhibits better wear resistance compared to the sheet with α fiber-{100}//ND.

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.

Self-sacrificial templating synthesis of flower-like nickel phyllosilicates and its application as high-performance reinforcements in epoxy nanocomposites

The nanocomposites of flower-like nickel phyllosilicate particles incorporated into epoxy resin were fabricated via an in-situ mixing process.The flower-like nickel phyllosilicate particles were firstly synthesized using a mild self-sacrificial templating method,and the morphology and lamellar structure were examined carefully.Several properties of mechanical,thermal and tribological responses of epoxy nanocomposites were performed.It was demonstrated that adequate flower-like nickel phyllosilicate particles dispersed well in the matrix,and the nanocomposites displayed enhanced tensile strength and elastic modulus but decreased elongation at break as expected.In addition,friction coefficient and wear rate were increased first and then decreased along with the particle content,and showed the lowest values at a mass fraction of 5%.Nevertheless,the incorporated flower-like nickel phyllosilicate particles resulted in the continuously increasing thermal stability of epoxy resin(EP)nanocomposites.This study revealed the giant potential of flower-like particles in preparing high-quality EP nanocomposites.

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.

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.