Anti-wear Ability Research Articles

In situ Synthesizing Carbon-Based Film by Tribo-Induced Catalytic Degradation of Poly-α-Olefin Oil for Reducing Friction and Wear.

Reducing friction and wear in a convenient and economical way has always been desired for industrial production. Here, a carbon-based film with excellent friction-reducing and antiwear abilities was formed in situ from the degradation of poly-α-olefin oil (PAO10) on the friction interfaces of the MoN/Pt coating sliding against the Si3N4 ceramic ball during the rubbing process. The MoN/Pt coating was prepared on stainless steel by direct current magnetron sputtering, in which an active 10 nm Pt layer grew well on the MoN layer. The MoN/Pt coating, lubricated by trace amounts of 5 mL PAO10 oil, exhibited a super low friction coefficient of 0.042 and an extremely low wear rate of 1.08 × 10-8 mm3 (N m)-1 after a long duration of applied friction under a high Hertz contact stress of 1.7 GPa. Raman spectra and transmission electron microscopy images revealed that the carbon-based film was composed of amorphous carbon phase dotted with sporadic Pt, MoO3, and SiO2 crystal phases. Molecular dynamics simulations illustrated that the MoN/Pt coating had catalytic action and resulted in the degradation of PAO10 during the rubbing process, which corresponded to the formation of the amorphous carbon-based film on the wear surfaces.

Improvement in friction and wear characteristics using CaF2 as a solid lubricant at different conditions

During machining, adequate cooling and lubrication is much needed to reduce friction, wear, and temperature by efficient heat dissipation resulting in improved surface quality and longer tool life. The various alternative approach developed to provide lubrication and cooling includes minimum quantity lubrication, cryogenic cooling, and machining with the use of solid lubricants. The efficiency of solid lubricant particles greatly depends on the particle size, the wt% of solid lubricant, and base fluid used to prepare a lubricant mixture. Therefore, an attempt has been made in the present investigation, to evaluate the tribological properties of CaF2 with different grain sizes and weight ratios in a base oil. Results demonstrated the anti-wear and friction ability of CaF2 as a solid lubricant by improving the tribological properties of sliding surfaces. An increase in friction coefficient is observed with larger grain size (30 and 50 μm) with 10 and 20 wt% of CaF2 as compared with 10 μm particle size. Results also showed the ability of solid lubricant particles with smaller particle sizes (10 μm) to maintain a thin film of lubrication. As a comparison, CaF2 mixed with a base oil performed equally well compared to MQL under different loading conditions. The reduction in friction coefficient and wear is observed with solid lubricant application due to its excellent lubricity even at higher load and pressure. The analysis shows the presence of wear on disc surface in the form of visible grooves and wear debris in dry and MQL condition whereas lubricating effects of CaF2 is dominant.

Excellent lubrication properties of 3D printed ceramic bionic structures

Three-dimensional (3D) printed ceramic structures loaded with lubricating materials could exhibit excellent lubrication effect. In this paper, various bionic petal structures and tree frog toe end structure of 3D-printed alumina (Al2O3) ceramic are designed to study the effects of lubricating structures and tungsten disulfide (WS2) solid lubricant on the friction performance. Compared to the friction properties of various bionic lubricating structures loaded with WS2, the bionic small petal structure with hexagonal arrangement exhibits a lowest friction coefficient of 0.411 and moderate wear resistance due to more storage of lubricant and debris. The maximum friction coefficient of 1.177 and optimum anti-wear ability are offered by the bionic tree frog toe end structure. In particular, the friction coefficient of the bionic petal lubricating structures loaded with WS2 are lower than that of blank printed Al2O3 ceramic, indicating that the lubricating structures provide positive effect on improving friction performance. Therefore, the 3D printed ceramic lubricating structures provided a novel strategy for achieving lubrication in advanced applications.

Fretting tribological behaviors of steel wires under lubricating grease with compound additives of graphene and graphite

Fretting damage among steel wires is an important cause for the fatigue fracture of wire rope. In this paper, firstly, the effect of carbon-based additives with different concentrations on the tribological performances of the special grease IRIS-200BB for wire rope was explored through a series of four-ball friction tests. Secondly, the fretting tribological behaviors of steel wires with helical structure under different lubrication conditions were studied by a self-made test rig. Results show that the anti-wear ability of the base grease is enhanced by the addition of multilayer graphene or micron graphite. In addition, micro-cutting on worn surface is obviously reduced when micron graphite and multilayer graphene are added into the base grease. For the convex friction form, the friction reduction and anti-wear performances of the base grease are effectively ameliorated by various additives, while for the concave friction form, tribological characteristics of the compound greases are inferior to that of the base grease.

Identifying the effects of cobalt addition in copper-graphene nanoplatelet composites towards improved tribological performance

Abstract Obtaining good affinity between graphene and copper in copper-graphene composites is the key to make full use of the good anti-wear ability of graphene. Copper-graphene nanoplatelets (Cu-GNPs) composites were prepared by ball-milling and hot pressed sintering with the addition of a small amount of cobalt to form intact graphene/cobalt/copper interfaces. The microstructural characterization shows that the GNPs are uniformly distributed on the grain boundaries of copper grains. The cobalt here acts as “binder”, bringing graphene and copper together efficiently. Benefiting from the unique structural design, Cu-GNPs composite doped with 0.25 wt % cobalt exhibits improved anti-wear performance with a stable friction coefficient of 0.246 and a small volume wear rate of 8.3 × 10−5 mm3/(N·m) (20% of that of pure copper composite). Excessive cobalt causes a significant increase of the structural defects in graphene and the formation of amorphous carbon, resulting in degradation of friction properties.

The Effect of α‐Zirconium Phosphate Nanosheets on Thermal, Mechanical, and Tribological Properties of Polyimide

AbstractIn this work, to investigate the addition effect of 2D α‐zirconium phosphate (α‐ZrP) nanosheets on the properties of polyimide (PI), a series of PI/ZrP composites are synthesized by in situ polymerization. The thermal, mechanical, and tribological properties of composites strongly depend on the dispersity and distribution of α‐ZrP nanosheets in the PI matrix. The dispersed α‐ZrP can make rich interfacial interactions with PI matrix, which facilitates the transfer of external stress, heat, antiwear ability, etc., from the PI matrix to the surface of the α‐ZrP nanosheets, leading to the obvious enhancements of the thermal, mechanical, and tribological properties of the PI/ZrP composites. Specially, compared with pure PI, the tensile strength and elongation at break of the optimum sample of PI‐0.6 are increased by 13.7% and 35.7%, while its wear volume is reduced by 85%. This work provides a new paradigm for using other layered 2D nanosheets to prepare high‐performance PI‐based composite materials.

Effect of Addition of Mo or V on the Structure and Cutting Performance of AlCrN-Based Coatings

This study focuses on a comparative analysis of AlCrXN (X = Mo or V) coatings with the reference AlCrN coating via arc ion plating technique (AIP). The XRD and XPS results showed that the AlCrXN coatings were mainly composed of fcc-(Cr,Al)N solid solution phases. Both the AlCrMoN and AlCrVN coatings exhibited much higher hardness and adhesive strength than the AlCrN coating. The addition of Mo or V decreased the coefficient of friction (COF) and wear rate, which was due to the formation of lubricant oxides containing Mo or V on the coating surfaces. The cutting results showed that abrasive wear, adhesive wear, and oxidation wear were the main wear mechanisms for the coated tools at the cutting speeds of 60 m/min and 94 m/min. The addition of Mo or V dramatically improved the cutting performance of AlCrXN-coated tools by increasing the anti-wear ability due to the high hardness and the formed lubricant VOx or MoOx films.

Effect of temperature on the rheological behavior of a new aqueous liquid crystal bio-lubricant

The rheological behavior of bis[(2-hydroxyethyl)ammonium] palmitate (DPA) fatty acid-derived ionic liquid crystal (ILC) and its dispersions in water has been determined. Neat DPA shows non-Newtonian behavior, with a temperature-thickening effect in the mesomorphic state. The dispersion of 1 wt% DPA in water yields a Newtonian fluid, with viscosity values close to that of water. In contrast, increasing DPA concentration to 2 wt% leads to non-Newtonian behavior, with a shear thinning effect at high shear rates. Rheo-microscopy, dynamic light scattering, Zeta potential and conductivity measurements show that the new Water+2%DPA dispersion presents sharp transitions in viscosity, transmitted light, turbidity, particles size, particle charge and conductivity in the critical temperature interval from 37 to 42 °C, at which neat DPA exhibits a transition from a solid phase to a liquid crystalline one. The tribological performance of Water+2%DPA has been studied at 37 °C, showing good friction reduction and excellent antiwear ability, without tribocorrosion. This lubricating behavior has been related to low viscosity, high conductivity, particle size reduction and bilayer organization with carboxylate groups oriented to the outer surface, in contact with the sliding materials. The results described here open the feasibility of developing new biocompatible aqueous lubricants with controlled temperature response.

Tribological evaluation and lubrication mechanisms of nanoparticles enhanced lubricants in cold rolling

Base oils containing different nanoparticles with varying concentrations are prepared, in which SiO2, TiO2 and ZnO (20 nm) nanoparticles are employed to improve the lubrication performance. Their tribological properties are evaluated on a ball-on-disk tribometer. The results show that the nano-additive lubricants exhibit a good friction reduction and anti-wear ability at the optimal concentration of 1.0 wt.%, in which SiO2 nanoparticles can reduce the coefficient of friction (COF) and the area of wear scar (AWS) by 45.6% and 35%, respectively. The SiO2 nanoparticles exhibit the best potential additive tested. The lubrication mechanisms of the nanoparticles can be attributed to the rolling, mending and the protective films.

Effect of Nano Alumina on the Properties of Fluorinated Polyurethane

This article selects studies on the preparation of fluorinated polyurethane-nano-alumina composite coating materials, and analyzes the anti-wear, water resistantance, and surface microstructure. Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) shows that the polyurethane synthesized in this study does not contain hydrophilic –CH2OH groups. The cavitation wear test depicts that the actual cavitation amount C of the Al2O3-FPU (4) (fluorinated polyurethane) coating is 0.9035 × 10−3 kg, and the anti-wear ability increases by 61.9% compared with FPU-0.5. The water-resistant test shows that the contact angle of water droplets on the surface of the coating increase from 95.3° of FPU-0.5 to 123.1° of Al2O3-FPU (4), and the water absorption decreases from 2.52% to 1.04%. Scanning electron microscopy (SEM) observation confirms that alumina particles can protrude on the coating surface and resist strong wear, while the C-F chain with high bond energy at the near-surface exhibits high strength and water resistance, which prevents wear from spreading deep into the coating. Differential scanning calorimetry (DSC) results show that the Tg(HS) value of the hard segment phase decreases with higher external force. Notably, when the coating is subjected to erosion, which enhances the crystallinity of the hard segment phase, the tensile strength of the hard segment phase of the coating surface is improved, which supports the wear resistance. Herein, we show that the addition of nano-alumina to fluorinated polyurethanes can control high water and abrasion resistance.

Enhanced anti-wear property of VCN coating in seawater with the optimization of bias voltage

Through multi-arc ion plating technology, the VCN coatings were successfully prepared under various bias voltages. The microstructure, mechanical property, anti-corrosion capability and tribological performance of these VCN coatings were comparatively studied. With the bias voltage increased from −25 to −100 V, the adhesion force and hardness of VCN coatings increased by 73.33% (22.5 to 39 N) and 14.83% (31.7 to 36.4 GPa). Besides, the toughness, corrosion resistance and anti-wear ability of VCN coatings were enhanced to varying degrees by changing the bias voltage. By contrast, the VCN coating at −100 V presented the smallest friction coefficient (COF) of 0.113 and wear rate of 5.25 × 10−7 mm3/Nm, implying an attractive protective effect for key friction parts in marine environment.

The tribology behaviors of textured graphite-like carbon film under air and aqueous environments

The pattern of micropore with various diameters (0, 0.5, 1.5 and 5 μm) on the surface of single crystal silicon was obtained through laser treatment and then the graphite-like carbon (GLC) film was deposited on these substrates through magnetron sputtering technology. The effect of micropore diameter on tribological performance of GLC film under air and aqueous environments was systematically investigated. The results indicated that the micropore diameter and test environment greatly affected the tribological behavior of GLC film. The friction coefficient (COF) and wear loss of GLC film were significantly improved in aqueous environment compared with in air. This was attributed to the formation of aqueous molecular film, which could obstruct the immediate contact between GLC film and counterpart. Meanwhile, the anti-wear ability of GLC film in aqueous environment strengthened firstly and then weakened as the micropore diameter increased. When the micropore diameter was 1.5 μm, the GLC film displayed the lowest wear rate of 0.32 × 10−8 mm3 Nm−1 in aqueous environment, which was 67.65%, 46.08% and 26.67% lower than the micropore diameters of 0, 0.5 and 5 μm, respectively. This was due to the synergistic effect of surface roughness and lubricant (graphitized particles and aqueous medium) captured by micropores.

Achieving high anti-wear ability of V–C–N coatings in seawater by carbon content design

The V–C–N coatings with various carbon contents were prepared by multi-arc ion plating method on 304 stainless steel and Si (100) substrates. The effects of carbon content on microstructure, mechanical behavior, tribological behavior and corrosion behavior of V–C–N coating were systematically evaluated. Results showed that the VC phase and amorphous phase were formed after the addition of carbon into VN coating. In the meantime, the critical load and hardness of V–C–N coating increased to 40 N and 36.5 GPa when the carbon content increased to 14.73 at%, respectively. Moreover, the incorporation of carbon could enhance the toughness, corrosion resistance and wear resistance of VN coating. By comparison, the V–C–N coating with 14.73 at.% C showed the lowest friction coefficient (COF = 0.12) and wear rate (7.2 × 10−7 mm3/Nm), implying a great potential for the protection of mechanical component in marine environment.

Preparation and tribological properties of a kind of lubricant containing cerium borate nanoparticles as additives

Oil-soluble compounds containing boron as lubricating additives were restricted by the hydrolysis of borate ester. In order to overcome this problem, cerium borate nanoparticles modified with oleic acid (O-CeB) as a potential substitute for conventional lubricant additive were studied in detail. The microstructures of the prepared nanoparticles were characterized. Tribological properties of cerium borate nanoparticles used as additive in base oil were evaluated, and the worn surface of the steel ball was investigated. The results show that O-CeB possesses better anti-wear ability at relatively higher concentration; in particular, it shows better friction-reducing ability under all these studied concentrations. Under higher load, its anti-wear property and friction-reducing property are better than that of Vanlube 289 in the base oil. Based on these results of interferometric surface profilometer and X-ray photoelectron spectroscopy, it can be deduced that a continuous resistance film containing depositions and the tribochemical reaction products was formed during the sliding process.

Experimental investigations of mechanical and tribological behaviours for organic and inorganic coatings deposited on mild steel substrate

ABSTRACTSurface treatment technologies are constantly evolving. Increasingly, surface functionalisation is of major concern to lighten structures, improve product performance and reduce costs. To fulfil its decorative and protective functions, it is essential that a coating adheres properly to its support. During the last few decades, many new deposition techniques have been developed and more and more tribological and corrosion resistant coatings have been made available. In this context, the present research has focused on two pneumatically sprayed epoxy/polyamide and inorganic silicate coatings which are deposited on the mild steel substrate. First, the main interest in this study is devoted to the analysis of the coating/substrate adhesion strength by using the squaring and pull-off tests. Second, the study has also focused on the analysis of friction and wear behaviours for the two systems of paint coatings under consideration by using a linear reciprocating tribometer under dry sliding condition. Experimental findings have shown that after appropriate surface preparation and degree of cleaning according to the standard ISO 8501-1, selected paint systems composed of organic or inorganic coatings effectively improve the service life of coated steel. Meanwhile, under the same sliding conditions, the wear results have revealed that the organic coatings have a higher anti-wear ability compared to the inorganic coatings. Thus, both organic and inorganic coatings play an important role in protecting the substrate against severe industrial environment. From the squaring and pull-off analyses, it has been deduced that scratch and pull-off behaviours of both coatings have been severely affected by the surface preparation, the number of protective layers and the thickness of coatings. In fact, the best adhesion, friction and wear properties are obtained for the paint system containing organic coatings where the third body is formed on the entire sliding strip in the test.

The Effects of Palm Oil with Nanoclay Additive in Hydrodynamic Journal Bearing Lubrication

In the present study, palm oil has been tested to study its capability as a lubricant to replace commercial mineral oil. To enrich the performance, nanoparticles additives were added. Previous studies proved that by adding the small size of additives into lubricating oil can lessen the friction and improve anti-wear properties. In this research, the size of the nanoparticle used was below 20nm. Four ball tester following ASTM D4072-94 was conducted to determine the optimum concentration of palm oil bio-lubricant with Nano-clay additive ranged from 0.02% to 0.08%wt. The results discovered that 0.04wt% of Nano-clay additive added into palm oil was the optimum concentration of the lubricant with the coefficient of friction 0.081, which recorded 16% reduction as compared to mineral oil (20W-40) – the reference lubricant. It also shows good anti-wear ability which the wear scar diameter was improved by 32%. The oil was then tested in journal bearing to characterize the hydrodynamic lubrication properties. The properties that have been observed were the coefficient of friction, pressure profile and temperature profile. The results showed that modified palm oil with Nano-clay provided better performance with low coefficient of friction (reduced more than 50% as compared to mineral oil) and also temperature profile (reduced up to 20% compared to mineral oil). As for the pressure profile, even slightly higher pressure recorded for palm oil due to lower viscosity, yet the pressure was improved with the presence of Nano-clay additive. In overall, it had been proven that palm oil with Nano-clay additive shows massive potential as an alternative lubricant to the same range with the current industrial mineral oil.

Engine Oil Degradation Induced by Biodiesel: Effect of Methyl Oleate on the Performance of Zinc Dialkyldithiophosphate.

In the present work, the oxidation stability of blends of methyl oleate, zinc dialkyldithiophosphate (ZDDP), and a high viscosity index mineral base oil was determined by the method of a rotating pressure vessel, while the antiwear abilities were evaluated on a four-ball friction tester. Thereafter, the thermal decomposition characteristics and oxidation products of the oxidized blends were analyzed by a thermogravimetric analyzer and a gas chromatograph coupled to a mass spectrometer, respectively. The results showed that the antioxidation ability of ZDDP was substantially improved by methyl oleate, while the antiwear capacity is markedly impaired by methyl oleate. Furthermore, the thermal decomposition characteristics and oxidation products of ZDDP-containing oils were altered by methyl oleate. The present study evidently convinced that chemical interactions between ZDDP and methyl oleate had occurred, which were attributed to the increased antioxidation ability and decreased antiwear capacity of ZDDP in oils contaminated with methyl oleate.

Experimental and CFD Simulation Studies on Bell-Type Air Nozzles of CFB Boilers

In this paper, a new bell-type air nozzle, which overcomes the structural defects of traditional bell-type air nozzles, is proposed and validated by cold test and numerical simulation. The pressure drop characteristic of the new bell-type air nozzle is measured. Furthermore, the causes of cover outlet abrasion and blockage, inner tube fracture, and irregular resistance change in traditional bell-type air nozzles applied in circulating fluidized bed (CFB) boilers are analyzed. Then, the performance of the new bell-type air nozzle is evaluated in a real CFB boiler, which is operated under regular working conditions. The results show that the new bell-type air nozzle has stronger anti-wear ability, excellent resistance characteristics, longer service life, and easier maintenance.

Tribological properties of oleylamine-modified nickel nanoparticles as lubricating oil additive

In order to improve the friction-reducing and anti-wear abilities of lubricating oil containing nickel nanoparticles as additive, nickel nanoparticles prepared by high energy ion beam evaporation (HEIBE) technique were modified by oleylamine on the surface. The morphology and microstructure of oleylamine-modified nickel nanoparticles showed that oleylamine was successfully attached to the surface of nickel nanoparticles. The friction-reducing and anti-wear properties of lubricating oil containing nickel nanoparticles and oleylamine-modified nickel nanoparticles as additive were investigated by four-ball tribometer. The addition of oleylamine-modified nickel nanoparticles into lubricating oil further reduced the friction coefficient and wear scar diameter of the steel balls lubricated by the base oil PAO6 and the engine oil CJ-4. Compared with the pure PAO6 oil, the mean friction coefficient and the mean wear scar diameter of the steel balls lubricated by PAO6 oil with the addition of nickel nanoparticles decreased by up to 32.6% and 15.3%, and that lubricated by PAO6 oil with the addition of oleylamine-modifiednickel nanoparticles decreased by up to 48.4% and 20.4%, respectively. Besides, the mean friction coefficient and the mean wear scar diameter of the steel balls lubricated by CJ-4 engine oil with the addition of 0.1 wt% of oleylamine-modified nickel nanoparticles decreased by 38.1% and 18.3% in comparison with the mean friction coefficient and the mean wear scar diameter of the steel balls lubricated by pure CJ-4 engine oil.

Structure, mechanical and tribological properties in seawater of multilayer TiSiN/Ni coatings prepared by cathodic arc method

The monolayer TiSiN and multilayer TiSiN/Ni coatings were deposited on the surface of Ti6Al4V alloy and Si wafer through cathodic arc method. By analysis, the TiSiN layer presented an amorphous/nanocrystalline structure. The adhesion force and toughness of multilayer TiSiN/Ni coatings could be significantly improved by the insertion of Ni layer. Meanwhile, the modulation ratio of Ni and TiSiN layers greatly affected the tribology behavior of multilayer TiSiN/Ni coatings in seawater. With the increase of modulation ratio, the anti-wear ability of multilayer TiSiN/Ni coating increased firstly and then decreased. When the modulation ratio was 1:5, the multilayer TiSiN/Ni coatings displayed the lowest friction coefficient (COF) of 0.14 and wear rate of 1.06 × 10−6 mm3/Nm in seawater, which was about 53.33% and 62.81% lower than that of monolayer TiSiN coating, respectively. This was mainly due to the complexity of penetration path caused by the multilayer structure and the inhibition of crack extension caused by the improvement of toughness.