Good Anti-wear Properties Research Articles

Synthesis of anodizing composite films containing superfine Al 2O 3 and PTFE particles on Al alloys

Anodized composite films containing superfine Al 2O 3 and PTFE particles were prepared on 2024 Al alloy using an anodizing method. The microstructures and properties of the films were studied by scanning electron microscopy, optical microscopy and X-ray diffraction. Friction wear tests were performed to evaluate the mechanical properties of the composites. Results indicate that the composite films with reinforced Al 2O 3 and PTFE two-particles have reduced friction coefficients and relatively high microhardness. The friction coefficient can be as small as 0.15, which is much smaller than that of an oxide film prepared under the same conditions but without adding any particles (0.25), while the microhardness can reach as high as 404 HV. When rubbed at room temperature for 20 min during dry sliding friction tests, the wear loss of the film was about 16 mg, which is about the half of that of the samples without added particles. The synthesized composite films that have good anti-wear and self-lubricating properties are desirable for oil-free industrial machinery applications.

Tribological and Mechanical Properties of Carbon Nanofiber-Filled Polytetrafluoroethylene/Polyimide Composites

The tribological and mechanical properties of carbon nanofiber filled polytetrafluoroethylene/ polyimide composites were studied in this paper. The effect of filler contents (0.5, 1, 1.5, 2, 2.5, 3 and 5 wt%) on the tribological and mechanical properties was examined. Also, the influence of various loads (100 N, 150 N and 200 N) and velocities (0.69 m/s and 1.4 m/s) on the tribological performance was investigated. The results show that the best friction and wear performance would obtained under different loads and velocities, which reduced by 56.7% (150 N, 1.4 m/s) and 72.6% (200 N, 0.69 m/s), respectively. And also, optimal mechanical properties were obtained. In comparison with the mechanical properties of polytetrafluoroethylene/polyimide composites, the tensile strength, elongation-to-break and impact strength of 1 wt% carbon nanofiber filled polytetrafluoroethylene/polyimide composites increased by 5%, 50% and 75%, respectively. The transfer films, worn surfaces and impact fracture surfaces were studied by scanning electron microscopy. The micrographs show that a proper content of carbon nanofiber is helpful for forming a smooth and continuous transfer film, which is essential for achieving good anti-wear property. Meanwhile, mechanical properties have been improved due to the interfacial interaction between the matrix and carbon nanofibers.

Comparative Studies on Tribological Behavior of Multiply-Alkylated Cyclopentane with other Liquid Lubricants for Various Frictional Materials

The friction and wear behavior of silicone oil 114(114SO), a linear perfluoroalkyl polyether Z-25, polyalphaolefin (PAO) and multiply alkylated cyclopentane (MAC) for five friction couples are evaluated using a SRV tester at room temperature and the tribological performances of MAC are compared with those of the other three liquid lubricants. The test results indicated that MAC exhibits better excellent friction reduction and anti-wear properties than the three other liquid lubricants when they are used to lubricate the friction couple materials of GCr15 steel vs. GCr15 steel, Si3N4 vs. Si3N4, and GCr15 steel vs. Si3N4 respectively. When being used to lubricate the friction couple materials of GCr15 steel vs. copper-tin alloy and GCr15 steel vs. 1Cr18Ni9Ti stainless steel at lower loads, MAC also has good friction reduction and anti-wear properties.

Facile Synthesis of Molybdenum Disulfide Micro-Spheres and the Tribological Properties in Liquid Paraffin

Well-dispersed MoS2 micro-spheres with the diameters of 0.5∼1.5 µm have been successfully synthesized via the extraction-solvothermal method. The ions were extracted into hexane by the extractant Cyanex 302 (di-(2,4,4-trimethylpentyl) monothiophosphinic acid) firstly, then the extracted solution was given solvothermal treatment to synthesize MoS2 at 150 °C for 24 hours. The obtained samples was characterized by XRD, EDS, SEM, TEM, and HRTEM technologies, respectively. Results indicated that Cyanex 302 acted as phase transferring agent, reductant, sulfur source and morphology-controlling agent in the whole procedure. Moreover, the tribological properties of liquid paraffin (LP) containing the as-prepared MoS2 micro-spheres were also evaluated on a four-ball machine and the chemical states of some typical elements on the worn surfaces were examined with XPS, showing that the MoS2 product was an excellent oil additive in LP with good anti-wear and friction-reducing properties.

Microstructure and properties of HVOF sprayed Ni-based submicron WS 2/CaF 2 self-lubricating composite coating

Ni-based submicron WS 2/CaF 2 self-lubricating composite coatings were produced on carbon steel substrate by high velocity oxygen fuel(HVOF) spray processing, and the microstructure and mechanical properties of the coatings were investigated. Non-uniform microstructure characterized by some pores and microcracks is observed in the produced composite coatings, which leads to low microhardness value, low adhesive strength and low frictional coefficient. For Ni45-5%CaF 2-10%WS 2 (mass fraction) and Ni45-10%CaF 2-5%WS 2 (mass fraction) coatings, under the test condition of load 40 N and speed 2 m/s, the friction coefficients obtained at room temperature are in the range of 0.35–0.48 and 0.31–0.41, respectively. The friction coefficients of two kinds of coatings increase to 0.4–0.63 and 0.35–0.46, respectively, at the test speed of 1 m/s. And the Ni45-10%CaF 2-5%WS 2 coating presents the minimum friction coefficient of 0.32–0.38 and good anti-wear properties at 400 °C.

Tribological properties and worn surface analysis generated by ashless and phosphorus-free additive in water-based lubricant

Two kinds of ashless and non-phosphorus water-based lubricant additives, dodecenyl succinic acid monoesters and sulphurized dodecenyl succinic acid monoesters, were synthesized from dodecenyl succinic anhydride. The anti-wear and friction-reducing properties of the synthesized additives were evaluated using a four-ball machine, and the worn surfaces were analysed by scanning electron microscopy and X-ray absorption near-edge structure (XANES) spectrocoscopy. The tribological results show that the two kinds of additives exhibit good anti-wear and friction reduction properties as well as or better than oleate, which is an important commercial lubricant additive. The XANES results indicate that the tribofilms mainly consist of adsorbed layers and tribochemical layers, and more sulphate and less sulphide in the films would result in lower friction coefficient. The XANES results also show that thriboheat has important influences on the tribofilms' formation. The mechanism of film formation is proposed.

Preparation and Antiwear Properties of Silver Sulfide Nanoparticles in Microemulsion

Ag_2S nanoparticles were prepared in two different W/O microemulsions,the structure and morphologies of as-prepared Ag_2S nanoparticles were characterized by means of X-ray powder diffraction (XRD),transmission electron microscope(TEM).The tribological propcrties of liquid paraffin containing Ag_2S nanoparticles were evaluated on a four-ball test machine,the worn steel surface morphology were analyzed by using of scanning electron microscope(SEM).Results show that Ag_2S nanoparticles synthesized in two microemulsions,i.e.isooctane/sodium oleate/n-pentanol/water solution(sampleⅠ) and liquid paraffin/Span 80-Tween 80/n-butanol/water solution(sampleⅡ)both possess monocline crystal structure,and exhibit an even grain distribution.They have average particle size of 18nm and 5nm,respectively.The antiwear tests show that Ag_2S nanoparticles dispersed in liquid paraffin processed from liquid paraffin/Span 80-Tween 80/n-butanol/water solution microemulsion exhibit good antiwear properties which can improve load carrying capacity of the base oil remarkably.

Synergistic lubricating effects of ZDDP with a heterocyclic compound

PurposeIn response to a plea to eliminate zinc dialkyldithiophosphate (ZDDP) in engine oil, or at least reduce it to 0.05 per cent, unfortunately no new antiwear additives to reduce ZDDP have been found until now. The aim of this paper, therefore, is to resolve these problems by designing a novel benzothiazole compound and using it as a performance‐enhancing agent for ZDDP.Design/methodology/approachA benzothiazole derivative containing dialkyldithiocarbamate (BSD) was synthesized. The antiwear and load‐carrying properties of the additive and their synergistic effects with ZDDP were evaluated by a four‐ball tester.FindingsThe additive BSD possessed good load‐carrying capacity, and exhibits good synergistic antiwear and load‐carrying properties with ZDDP. The tribo‐chemical mechanism was also proposed.Originality/valueThe paper provides a good ashless additive which has good antiwear properties, and fulfils an identified resources need, which can offer practical help in industrial applications and also to an individual starting out on an academic career.

Synthesis and characterization of Bi–Pb–Sn alloy nanocrystals and their tribological performances

In this paper, Bi–Pb–Sn nanocrystals were prepared directly from bulk Bi, Pb, Sn grains through solution dispersion. The obtained Bi–Pb–Sn nanocrystals possess the similar crystal structure as that of Bi single-component metal and have an average particle diameter of 30 nm. Tribological results indicate that Bi–Pb–Sn nanocrystals as lubricating additives show good antiwear properties. In addition, the formation mechanism of the Bi–Pb–Sn nanocrystals was also discussed.

Tribological study of novel S–N style 1,3,4-thiadiazole-2-thione derivatives in rapeseed oil

Two non-phosphorus and ashless 1,3,4-thiadiazole-2-thione derivatives, 5-dodecyldithio-3-phenly-1,3,4-thiadiazole-2-thione (DPTT) and 5-cetyldithio-3-phenyl-1,3,4-thiadiazole-2-thione (DHTT), were synthesized and their tribological behaviors as additives in rapeseed oil (RSO) were evaluated using a four-ball friction and wear tester. Their thermal stabilities and anticorrosive properties were investigated. The results indicate that the additives possess good thermal stabilities, corrosion inhibiting abilities and excellent load-carrying capacities. Moreover, they both have good anti-wear and friction-reducing property at relatively low concentration and under all test loads. The worn surfaces of the steel balls were observed using a scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). It is supposed that the synthetic additives adsorb and react with the steel surfaces during the rubbing process and generate a surface protective film composed of sulfate, sulfide, iron oxide and organic nitrogen-containing compounds, which accounts for the better tribological behaviors of the base stock containing the synthetic additives as compared with the base stock alone.

Synthesis of water-soluble carbon nanotubes via surface initiated redox polymerization and their tribological properties as water-based lubricant additive

Polyacrylamide (PAM)-grafted multi-walled carbon nanotubes (MWCNTs-g-PAM) which are dispersable in water were prepared by the surface initiated redox polymerization of acrylamide using ceric ammonium nitrate (CAN) as initiator. They are soluble in polar solvents such as water, tetrahydrofuran and acetone. The chemical structure of the resulting product and the quantities of grafted polymer were determined by FT-IR, TGA. TEM, and FE-SEM observations indicated that the nanotubes were coated with a PAM layer, exhibiting core-shell nanostructures, with the PAM chains as a brush-like or hairy shell, and the MWCNTs as a hard backbone. Furthermore, the tribological properties of the prepared MWCNTs-g-PAM composites as an additive in water were evaluated with a four-ball machine. The results confirmed that the composites exhibit good anti-wear and friction reduction properties as well as load-carrying capacity. This was attributed to the possibility of the composites acting as nanometer sized tiny bearings during lubrication.

Review of boundary lubrication mechanisms of DLC coatings used in mechanical applications

In the last ten years significant progress has been made on development and understanding of diamond-like carbon coatings (DLC), which enabled them to become one of the most promising types of protective coatings for various mechanical applications. Their main advantages are low friction, good anti-wear properties, and adhesive protection. However, due to their low surface energy their reactivity with conventional oils and additives is limited, which makes achieving effective boundary lubrication a complex task. For a qualitative step-change that would improve the performance and allow effective optimizing and tailoring of these boundary-lubricated tribological systems, it is necessary to understand the mechanisms of why, how, under which conditions, and with which materials and lubricants, the actual boundary lubrication is possible—if at all. The current results on boundary lubrication of DLC coatings are not many, and are due to the different types of coatings, lubricants and additives used in these studies, often difficult to compare and sometimes even contradictive. However, a recent great demand in different industries to apply the DLC coatings to lubricated systems requires a better understanding of these phenomena and overall performance. Therefore, if we wish to see a more effective continuation of the research and a better understanding of the scattered results, an overview of today’s state-of-the-art of lubricated DLC contacts is needed. In this paper we analyse the behaviors and suggested mechanisms from already-published studies and we summarize the present understanding of the boundary lubrication of DLC coatings. We focus on the DLC-lubricant interaction, thus we analyse only self-mated DLC/DLC contacts in order to avoid the inevitable effects from interactions with other counter materials such as steel.

Sliding Friction Behaviors of Poly (p‐Phenylene Benzobisoxazole) (PBO) Film under Different Conditions

Poly (p‐phenylene benzobisoxazole) (PBO) was synthesized and fabricated into film via a hot‐press technique. The tribological properties of this PBO film sliding against steel were studied using two types of tribometer, and the effects of applied load, sliding speed, and ambient temperature on its tribological properties were investigated. It was found that PBO formed a layered structure during the hot‐press process as it has a rigid molecule and exhibits lyotropic liquid crystalline behavior. This unique structure along with the excellent heat and chemical resistance provided a relatively low friction coefficient of about 0.20 and a good antiwear property (a specific wear rate of 1.6×10−15 m3/N · m), making it a promising material for application in the tribological fields.

Tribopolymerization of n-butyl acrylate on the steel–steel rubbing surface

Antiwear property of n-butyl acrylate (BA) in hexadecane for steel–steel friction elements was studied. Scanning electronic microscopy (SEM) images of worn scars of balls, and width measurements of worn tracks of disks indicate that BA has good antiwear property. Tribopolymerization (polymerization initiated by the rubbing surface) tests of BA used as lubricant instead of an additive were conducted, to classify antiwear mechanisms. Infrared spectroscopy (IR) of washing solution and thermogravimetry (TG) traces of wear debris confirmed that tribopolymers were generated on steel–steel interface in situ. Also considerable wear products were precipitated from vacuum-condensed worn fluids with methanol as the non-solvent, characterized by IR, gel permeation chromatography (GPC), nuclear magnetic resonance (NMR) spectroscopy, showing that the precipitates were poly( n-butyl acrylate) (PBA) with very high molecular weight. To study tribopolymerization mechanisms of BA, effects of sliding velocities and adding 1 wt% n-butyl alcohol to BA fluids on the mass of tribopolymers were investigated, respectively. Expectedly, the mass of tribopolymers dramatically enhanced with the sliding velocity increasing, showing that the tribopolymers were generated just due to friction processes. Additionally, tribopolymerization of styrene (easy to thermopolymerize) was studied. Unexpectedly—but not unreasonably—no substantial worn products were precipitated from vacuum-condensed worn fluids. Based on these experimental results, an exoelectron-radical-tribopolymerization mode, consistent with some Kajdas’ tribochemistry theories, for BA was proposed.

Preparation and characterization of poly(phthalazinone ether ketone)/SiO2 hybrid composite thin films with low friction coefficient

Organic–inorganic poly(phthalazinone ether ketone) (PPEK)/SiO2 hybrid composite thin films were prepared by the dip-coating method on pre-cleaned glass substrates. The covalent bonds between organic and inorganic phases were introduced by an in-situ O-acylation reaction of isocyanatopropyltriethoxysilane (ICPTES) with the borohydride-reduced PPEK forming a polymer bearing triethoxysilyl groups. Theses groups were subsequently hydrolyzed with tetraethoxysilane (TEOS) and allowed to form a network via a sol–gel process. The polymer hybrid composite exhibited good thermal stability and a higher glass transition temperature as compared with the pure resin. Atomic force microscope, water contact angle measurement and scanning electron microscope were used to characterize the polymer hybrid thin films. The tribological experiment showed that the films have very low friction coefficient (about 0.1) and good anti-wear properties, without failure even after sliding for 18,000 s under modest loads. The improved tribological properties of the modified substrate were attributed to good adherence of PPEK/SiO2 hybrid films on the substrate and synergy of both PPEK matrix and silica particles.

Ester hydroxy derivatives of methyl oleate: Tribological, oxidation and low temperature properties

Five branched oleochemicals were prepared from commercially available methyl oleate and common organic acids; and their lubricant properties were determined. These branched oleochemicals are characterized as 9(10)-hydroxy-10(9)-ester derivatives of methyl oleate. These derivatives show improved low temperature properties, over olefinic oleochemicals, as determined by pour point and cloud point measurements. The derivatization also increased thermo-oxidative stability, measured using both pressurized differential scanning calorimetry (PDSC) and thin film micro oxidation (TFMO) methods. Branched oleochemicals were used as additives both in soybean oil and in polyalphaolefin. Their lubrication enhancement was evaluated by both four-ball and ball-on-disk wear determinations. These derivatives have good anti-wear and friction-reducing properties at relatively low concentrations, under all test loads. Their surface tensions were also determined and a trend was observed. The materials with larger side chain branches had lower surface tension than those containing smaller side chain branches. An exception to this trend was found when studying the compound with the carbonyl containing levulinic acid side chain, which had the highest surface tension of the branched oleochemicals studied. Overall, the data indicate that some of these derivatives have significant potential as a lubricating oil or fuel additives.

Tribological Behaviors and Film Analysis of Two Ashless Phosphorus/Sulfur-Containing Additives in Rapeseed Oil

Two synthetical ashless phosphorus/sulfur-containing compouds were used as additives in biodegradable rapeseed oil (RSO). Their anti-wear and friction-reduction performances as lubricating oil additives were evaluated using four-ball tester. The chemistry of their tribofilms and thermal films was analyzed with X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge spectroscopy (XANES), The results showed that the two phosphorus/sulfur-containing compounds possessed rather good anti-wear properties and friction-reducing performances. According to the XPS and XANES analytic results, the tribofilms and thermal films generated from the additives were mainly composed of adsorbed-film and reaction film, in which phosphate and pyrophosphate were main existence form of P, FeSO4 was the main existence form of S. The results also showed that tribo-heat played different roles in the formation of tribofilms generated from the two different additives.

Anti-Wear Performance and Chemical Property of Films of Nitrogen-containing Heterocyclic Lubricating Oil Additive

Two ash-less and phosphorous-free nitrogen-containing heterocyclic anti-wear additives (N-di-isooctyl-2-benzothiazolesulfenamide, DIMB and (2-sulfurone-benzothiazole)-3-methyl-isooctyl thiohydroxy acetate, MBES) were synthesized. Their anti-wear and friction-reduction performances as lubricating oil additives in groupⅢ base oil were evaluated using SRV high temperature friction and wear tester. The chemistry of their tribofilms was analyzed with X-ray absorption near-edge spectroscopy (XANES), and atomic force microscopy (AFM) was then used to examine the general morphology of the reaction films. The results showed that the two nitrogen-containing heterocyclic compounds possess rather good anti-wear properties, but no friction-reducing performance. According to the XANES analytic results, the tribofilms generated from the additive MBES were mainly composed of FeSO4, whereas the films generated from the additive DIMB mainly contained FeS2. The AFM images revealed that in comparison with the worn surfaces from zinc dialkyldithiophosphate (ZDDP), the worn surfaces from the additives DIMB and MBES, respectively, presented large and deep grooves.

Preparation and Antiwear Property of Monodisperse Silver Nanoparticles in Microemulsion

Monodisperse Ag nanoparticles were prepared in quaternary W/O microemulsions containing Span 80-Tween 80,liquid paraffin and 1-butanol.It was found that mass ration of Span 80 and Tween 80 had an obvious effect on the morphology and size distribution of the Ag nanoparticles.Morphologies,structure and thermal properties of the silver nanoparticles were characterized by means of X-ray diffraction(XRD),transmission electron microscopy(TEM),Fourier transform infrared(FT-IR),thermogravimetry(TG)and differential thermal analysis(DTA).The results show that the Ag nanoparticles have cube crystal structure;exhibit uniform size distribution and have an average size of 6 nm at the mass ratio of Span 80∶Tween 80=7∶3;and are coated with long chain fatty acid through carboxyl.H2O and 1-butanol in microemulsions were removed through vacuum distillation,and Ag nanoparticles were dispersed stably in liquid paraffin.The tribological properties of liquid paraffin containing Ag nanoparticles were evaluated on a four-ball test machine.Results showed that the Ag nanoparticles in liquid paraffin exhibited good antiwear property and could improve load carrying capacity of base oil remarkably.

Tribological behaviors of surfactant-functionalized carbon nanotubes as lubricant additive in water

The multi-walled carbon nanotubes (MWCNTs) are functionalized by self-assembled surfactant layers after sonication in anionic surfactant sodium dodecyl sulfate (SDS) aqueous solution. The tribological properties of the SDS-functionalized MWCNTs as additive in water-based lubricants were evaluated with a four-ball tester. The results show that the SDS-functionalized MWCNTs exhibit good anti-wear and friction reduction properties as well as enhanced load-carrying capacity. The maximum non-seizure load (PB value) can be raised about 3–7 times when SDS-functionalized MWCNTs were added into water. The mechanism of SDS-functionalized MWCNT additive was investigated with scanning electron microscopy (SEM), Auger electron spectroscopy (AES), and Raman spectroscopy. These preliminary results show a promise in applications of surfactant functional carbon nanotubes as an additive in water.