Significant Improvement In Tribological Properties Research Articles

Improving the tribological performance of polyphenylene sulfide by incorporating irradiation treated polytetrafluoroethylene powders

AbstractIn this work, the efficacy of using irradiation treated polytetrafluoroethylene (i.e., i‐PTFE) powders on the tribological properties of polyphenylene sulfide (PPS)‐based composites was systematically investigated. The results showed that the addition of i‐PTFE powders significantly improved the friction and wear properties of PPS. The average friction coefficient and specific wear rate of PPS/i‐PTFE 20 wt% composite reached 0.129 and 1.75 × 10−5 mm3 N−1 m−1, which were 77.4% and 99.5% lower than those of pure PPS, respectively. SEM observations indicated that the i‐PTFE powders exhibited a relatively uniform distribution within PPS, which favored the formation of intact, uniform and continuous transfer film on the surface of friction pair, thereby resulting in a significant improvement of tribological properties for PPS/i‐PTFE composites. The worn surface of the testing specimen turned smoother and the wear debris became smaller with increasing addition of i‐PTFE powders, which was related to the improvement of tribological performance by forming transfer film at the sliding interface. This work provided a strategy to fabricate high performance self‐lubricating polymer composites that demonstrate potential applications in engineering sectors.

High temperature tribological properties of NiAl-Ag2Mo2O7 composite coatings prepared by spark plasma sintering

NiAl-Ag2Mo2O7 composite coatings were prepared with different contents of Ag2Mo2O7 (0– 15 wt%) by spark plasma sintering (SPS) technology, in which Ag2Mo2O7 was synthesized through hydrothermal method. The mechanical and tribological properties of the composite coatings were investigated from room temperature (RT) to 800 °C, and the corresponding lubrication mechanisms were also revealed. The results show that Ag2Mo2O7 is decomposed into Ag, MoO3 and Mo2C phases during sintering process. NA10 (NiAl-10wt%Ag2Mo2O7) presents excellent tribological properties, especially at 800 °C, the friction coefficient and wear rate reach the lowest value of 0.29 and 6.15 × 10−5 mm3/(N·m), respectively. The significant improvement of tribological properties is attributed to the formation of a synergistic lubricating glaze layer composed of NiO, NiMoO4, Ag2MoO4 and Ag2Mo2O7 by tribo-chemical reaction on the worn surface.

Fabrication of permanent self-lubricating 2D material-reinforced nickel mould tools using electroforming

In the replication of polymeric micro/nano structures, adhesion and friction between mould tool and polymer cause significant feature failure. For the first time, this work developed a novel strategy for the fabrication of high-hardness and self-lubricating 2D material-reinforced nickel mould tools using electroforming to achieve high precision replication of polymeric micro structures. In this study, layered 2D material, including graphene oxide (GO), molybdenum disulfate (MoS2), and tungsten disulfide (WS2), for the fabrication of self-lubricating mould tools, were systematically studied. Our results demonstrated that nickel/WS2 mould tools, followed by nickel/GO and nickel/MoS2 mould tools, presented the most significant microhardness improvement. A maximum microhardness of ∼660 HV together with a minimum crystallite size of 12 nm was achieved from 0.5 g/L WS2, indicating a 3.67 times microhardness increase and 3 times crystallite size reduction relative to the pure nickel mould tool. The enhanced microhardness can be attributed to the 2D material-induced crystal refinement, and inherent hardness and incorporation content of 2D material. Additionally, friction and wear tests revealed that a low concentration of WS2 at 0.14 g/L achieved the lowest coefficient of friction (COF) and superior wear resistance. The COFs in the initial stage and steady state stage were 0.08 and 0.18, respectively, implying decreases of 42.8% and 72.3%, respectively, and a 27-fold increase in lifetime compared with those of the pure nickel mould tool. Such a significant improvement in tribological properties was due to the formation of self-lubricating transfer film by the interlayer shear effect of few-layered 2D material nanosheets. Finally, defect-free polymeric microfluidic chips were micro hot embossed using an optimal self-lubricating nickel/WS2 mould tool for validation. This work provides significant insight into the fabrication of potential self-lubricating micro/nano mould tools for microfluidics applications.

Synergistic effect of binary systems of nanostructured MoS2/SiO2 and GO/SiO2 as additives to coconut oil‐derived grease: Enhancement of physicochemical and lubrication properties

AbstractThe present work addresses the use of synergistic blends of two different types of nanomaterials (spherical particles and lamellar sheets) as additives for coconut oil‐based grease formulation to provide the energy‐efficient and sustainable alternative to conventional grease. The spherical SiO2 nanoparticles are separately blended with 2D lamellar sheets of MoS2 and graphene oxide (GO) in variable ratio and probed their synergistic effects for enhancement of physicochemical and lubrication properties. The SiO2 nanoparticles, MoS2, and GO nanosheets are prepared by modified sol–gel, hydrothermal reduction, and Hummer's methods, respectively. The 0.05 wt% nanomaterials blends of MoS2/SiO2 (30:70) and GO/SiO2 (50:50) as optimised doses furnished the maximum reduction in the friction and wear. The combination of rolling friction and low shear properties using the synergistic blend of the spherical nanoparticles (SiO2) and nanosheets (MoS2 and GO) showed significant improvement in tribological properties. The optimised blends of nanoadditives, that is, MoS2/SiO2 and GO/SiO2 conserved the energy by 20% and 19%, respectively. These findings suggest that the use of synergistic blends of variable nanomaterials to vegetable oil‐based lubricants can pave a direction for new generation lubricant formulation, where environmental sustainability and energy conservation are on prime importance.

Effect of cryogenic treatment on tribological behavior of Ti6Al4V alloy fabricated by selective laser melting

Ti6Al4V fabricated by selective laser melting (SLM) is commonly used as an artificial hip joint. However, the inferior tribological properties fall far short of the requirements for biomedical engineering and is harmful to the patients. In this study, cryogenic treatment (CT) was proposed to solve this problem. CT at −196 °C with a soaking time of both 2 h and 72 h were conducted, and their tribological properties were investigated by microstructure observation, Vickers hardness, and wear tests. The results showed that the microstructure of the as-fabricated and cryogenic treated (CTed) for 2 h are mainly composed of acicular martensite (α′ phase). However, the microstructure is transformed into alpha and beta phases after CT for 72 h. Vickers hardness of the specimens as-fabricated, CTed for 2 h and 72 h are 390.79 HV, 388.03 HV, and 371.34 HV, respectively. CT induces a significant improvement in tribological properties, which is correlated with the microstructure evolution. A similar wear mechanism can be observed for the specimens as-fabricated and CTed for 2 h, which is the co-action of severe abrasive wear, adhesive wear, and fatigue wear. While the specimen CTed for 72 h is slight abrasive wear mechanism.

Investigation of graphite effect on the mechanical and tribological properties of Al 7075-SiC-graphite hybrid metal matrix composites

The aluminium metal matrix composite reinforced with ceramic material of Silicon carbide (SiC) has good mechanical properties. However, aluminium based ceramic composites require improvements in their lubrication and tribological properties. In this study an attempt is made in the development of a new material through powder metallurgy technique by the addition of Graphite, which acts as a solid lubricant. This work investigated the influence of graphite on the wear behaviour of Al 7075/SiC /X wt.% graphite(X=0, 5 and 10) hybrid composite. The investigation reveals the effectiveness of incorporation of graphite in the composite for gaining wear reduction. The Al 7075 (aluminium alloy 7075) reinforced with SiC –graphite were investigated. The composites were fabricated using powder metallurgy route. The microstructures, material combination, wear and friction properties were analysed by scanning electron microscopy, XRD, and pin-on-disc wear tester. The newly developed aluminium composite has significant improvements in tribological properties with a combination of 5% Silicon carbide (SiC) and 5% Graphite. The test reveals that sliding distance of 1000 m and sliding speed of 1.5 m/s with applied load of 5 N result in minimum wear loss of 0.01062g and coefficient of friction as 0.1278.

Evaluation of mechanical and frictional properties of CuO added MgO/ZTA ceramics

The focus of the present work is to investigate the tribological effect of adding CuO as solid lubricant in MgO/ZTA (Magnesia-Zirconia Toughened Alumina) ceramics. Different wt% of CuO (0–5 wt%) have been added in MgO/ZTA ceramics using powder metallurgy process route to study the change in mechanical properties i.e., hardness, fracture toughness and flexural strength, as well as the tribological properties i.e., coefficient of friction (COF) and wear depth, against corundum alumina balls. The addition of CuO shows significant improvement in tribological properties but a diminishment of the mechanical properties. A significant reduction of 53.45% in COF with minimum wear depth is achieved with the addition of 1.5 wt% CuO inside the MgO/ZTA matrix. The improvement in COF and specific wear rate of the composite is observed with increasing sliding velocity due to the presence of uniform patchy layer along with a glossy surface on the wear track. The formation of patchy layer is enhanced with an increase in sliding velocity due to high squeezing and smearing of wear debris. A significant increment in specific wear rate is observed with increasing load due to the delamination process prevailing at the contact surfaces.

Mechanical and tribological properties of Al 7075 /SiC/ Graphite hybrid composites processed by powder metallurgy technique

The metal matrix composite strengthened with ceramic material of carbide (SiC) has smart mechanical characteristics. Metal-based composites, however, demand progress in their friction and tribological characteristics. In this work-study an effort is made to design a completely new material through the method of metallurgy by adding graphite, which acts as a solid lubricant. This study explored the effect of graphite on the tribological behaviour of hybrid composite Al 7075/5 wt. % SiC / X wt. % graphite (X=10, 5 and 0). The research confirms the performance of wear properties by incorporating graphite into the composite. The sic-graphite reinforced Al 7075 (aluminium alloy 7075) was studied. Metallurgy route was used to prepare the composites. Microstructures, the mixture of materials, wear and wear resistance properties were analyzed by optical micro cope and scanning electron microscope, XRD, and pin-on-disc apparatus. The freshly developed metal composite has significant improvement in tribological properties with a mixture 5% silicon carbide (SiC) and 5% graphite. The experimental investigations confirm that a sliding distance of one thousand meters and a sliding velocity of 1.5 m / s with an applied load of 5 N leads to minimum wear loss of 0.01062g and coefficient of friction as 0.1278

Investigation of tribological properties and engine performance of polyol ester–based bio-lubricant: Commercial motorbike engine oil blends

This article explores the influence of blending polyol ester–based bio-lubricant with commercial lubricant on engine performance. Polyol esters trimethylolpropane ester and pentaerythritol ester were prepared from Calophyllum inophyllum seeds. Extreme care was taken to minimize deterioration of physicochemical properties when blending bio-lubricant with commercial oil. Blending of bio-lubricant with commercial oil was carried out in 10%, 15%, 20% and 25% volume. The test oils were first investigated for wear and friction properties on a four-ball wear tester. Optimum blending ratio was calculated from results of tribological properties, and the blend with optimum blend ratio was investigated for engine performance. The engine performance of the optimum blends was evaluated by conducting a 60-h endurance test on a motorbike. Significant improvement in tribological properties was observed up to a blending percentage of 15% when blending pentaerythritol ester with commercial oil. In the case of trimethylolpropane ester–based bio-lubricant, 10% blending with commercial oil gave optimum performance. The novel evaluation of engine performance of commercial oil and blends has shown a reduction in the wear of engine components with an encouraging decrease in fuel consumption. Metallographic studies conducted on worn piston rings reveal synergy between additives in the commercial oil and esters in the bio-lubricant in reducing wear and friction, thereby reducing fuel consumption.

Tribological properties of water-based drilling fluids with borate nanoparticles as lubricant additives

In this work, several nanostructured borates such as magnesium, zinc, aluminum and titanium borates were synthesized. These borates were added to drilling muds and their ability to improve tribological properties of water-based drilling fluids, was investigated. The tribological properties of the fluids containing these nano-additives were compared with those of a typical mud (containing bentonite and water) with and without a commercial lubricant additive (BitcLub, M − I SWACO) as reference samples. The results indicated that adding nano-additives to the drilling mud increased its extreme pressure property by more than five times compared to the reference samples. At the same time, these nano-additives decreased the coefficient of friction due to their good ability in producing a strong protective film (tribo-film) on the contacting surfaces being stable at extremely high pressure and temperature conditions. Among all the prepared nano-additives, titanium borate, which is biodegradable, showed a significant improvement in tribological properties of drilling fluid as compared to the other borates.

THERMAL, MECHANICAL, AND TRIBOLOGICAL PROPERTIES OF PTFE COMPOSITE WITH 20% GRAPHITE CONTENT IRRADIATED WITH AN ELECTRON BEAM

The paper investigated the effect of irradiation with an electron beam of energy 10MeV in doses of 26-156 kGy on polytetrafluoroethylene with a 20% graphite additive. The tests have shown that changes in thermal properties of the composite (heat of crystallization, melting point and degree of crystallinity) directly affected mechanical properties and contributed to the significant improvement of tribological properties. Tribological tests were performed on a pin-on-disc (T-01) test stand and counter-specimens were made of 1H18N9T steel. The load applied in the friction pair was 1 and 2 MPa (20 and 40 N). A nearly fourfold reduction in linear wear compared to the initial state for a load of 1 MPa has been shown. On the other hand, a more than 20-fold decrease in wear was found during tribological tests when the load was increased to 2 MPa. The most advantageous results were obtained for specimens irradiated with a dose of 104 kGy; irradiation with a higher dose led to degradation of the polymer and caused its wear to increase again. The obtained results hold promise for a significant improvement of the operational life of friction couples which do not require lubrication, used for example in air compressors and engines, and for the possible application of thus modified polymers in nuclear and space industries.

Re-Melting Technique with High Intense Pulsed Plasma Beams Applied for Surface Modification of Steel - Own Investigations

The plasma beams were generated in a Rod Plasma Injector (RPI) operated in the Deposition by Pulsed Erosion (DPE) and Pulse Implantation Doping (DPE) modes. Samples of unalloyed and austenitic stainless steels were irradiated with short (μs scale) intense (energy density 2.0-5.0 J/cm2) pulses. The near surface layer - thickness in μm range - was melted and simultaneously doped with active element like nitrogen, cerium and lanthanum. Heating and cooling processes were of non-equilibrium type. The most important obtained results were: (i) austenitic structure was present in unalloyed steels after HIPPB modification processes and (ii) modified surface layers of austenitic stainless steel showed significant improvement of tribological properties and increase of high temperature oxidation resistance as compared with initial material.

Tribological behaviors of internal plasma sprayed TiO2-based ceramic coating on engine cylinder under lubricated conditions

TiO2-12wt% Al2O3 coating was deposited on engine cylinder surface by internal plasma spraying to optimize the cylinder-piston tribosystem. The tribological tests were conducted under lubricated conditions on SRV4® reciprocating tribometer. To simulate engine acceleration from cruise to full power, friction parameters of load, frequency and temperature were designated to change over a wide variation, namely 53–157N, 35–45Hz and 85–197.5°C respectively. Accordingly, triboscopic 4D-maps were plotted originally to exhibit the evolution of friction coefficient. Results also showed that cylinders after coating had significant improvement of tribological properties compared with the uncoated specimens, which can be attributed to the great chemical stability to oil, smooth surface roughness during friction, high hardness and H/E of the ceramic coating.

Study of tribological properties on Al/Al2O3/MoS2 hybrid composite processed by powder metallurgy

Aluminium ceramic composites with improved mechanical and chemical properties are essential and needed in aerospace and automotive application. The aluminium matrix composite reinforced with ceramic material of alumina (Al2O3) has good tribological properties. However, aluminium based ceramic composites require improvements in their lubrication properties. In this study an attempt is made in the development of a new material through powder metallurgy technique by the addition of molybdenum disulphide (MoS2), which acts as a solid lubricant. This molybdenum disulphide (MoS2) based solid lubricant has unique advantage that it can be used in vacuum space, but the same is not applicable in case of graphite. The microstructures, material combination, wear and friction properties were analysed by scanning electron microscopy, EDX, and pin-on-disc wear tester. The newly developed aluminium composite has significant improvements in tribological properties with a combination of 5% alumina (Al2O3) and 5% molybdenum disulphide (MoS2). The test reveals that sliding distance of 1000m and sliding speed of 1.5m/s with applied load of 5N result in minimum wear loss of 0.0102g and coefficient of friction as 0.117.

Improving tribological properties of Ti-5Zr-3Sn-5Mo-15Nb alloy by double glow plasma surface alloying

Molybdenum, an alloying element, was deposited and diffused on Ti-5Zr-3Sn-5Mo-15Nb (TLM) substrate by double glow plasma surface alloying technology at 900, 950 and 1000°C. The microstructure, composition distribution and micro-hardness of the Mo modified layers were analyzed. Contact angles on deionized water and wear behaviors of the samples against corundum balls in simulated human body fluids were investigated. Results show that the surface microhardness is significantly enhanced after alloying and increases with treated temperature rising, and the contact angles are lowered to some extent. More importantly, compared to as-received TLM alloy, the Mo modified samples, especially the one treated at 1000°C, exhibit the significant improvement of tribological properties in reciprocating wear tests, with lower specific wear rate and friction coefficient. To conclude, Mo alloying treatment is an effective approach to obtain excellent comprehensive properties including optimal wear resistance and improved wettability, which ensure the lasting and safety application for titanium alloys as the biomedical implants.

Evaluation of Mechanical Properties of Aluminium Alloy Reinforced with Silicon Dioxide and Fly Ash Hybrid Metal Matrix Composites

The present study focus at evaluating the mechanical properties of Aluminium in the presence of silicon dioxide, fly ash and its combinations. The compositions were added up to the required level and stir casting method was used for the development of aluminium metal matrix composites. Structural characterizations were carried out on metal matrix composites by x-ray diffraction methods and optical microscopy was used for the micro structural studies. The mechanical properties of metal matrix composites like tensile strength and hardness tests were carried out. Wear test was also performed using pin on disc. In the presence of silicon dioxide and fly ash (0–10%) with aluminium matrix, it was fairly observed that the densities of the composites were decreased and the hardness was increased. Correspondingly, the decrease in tensile strength was observed with decrease in addition of reinforcement. The aluminium-SiO2-fly ash hybrid metal matrix composites extremely differed in all of the properties measured. The newly developed aluminium hybrid composites have significant improvements in tribological properties with a combination of silicon dioxide and fly ash.

Self-Organization of Friction Surface of Fe-Mn-C-B Coating With Increased Resistance to Abrasion / Samoorganizacja Powierzchni Tarcia Powłoki Fe-Mn-C-B O Zwiększonej Odporności Na Zużycie Ścierne

The paper concerns the research on self-organization of the surface of coating of hypoeutectic alloy Fe-Mn-C-B modified Si, Ni, Cr, Cu with friction with C45 steel. The coatings were obtained by arc welding using a flux-cored wire. Tests of resistance to wear were carried out for hypoeutectic coatings with use of the friction pair pin-on-disc in the conditions of sliding friction, in model lubricating environments. The surface-active (glycerol oil) and inactive (Vaseline grease) lubricant was used. Tribological tests carried out showed that cooperation of hypoeutectic alloy coating with counterbody of C45 steel with lubrication with surface-active lubricant results in a significant improvement in tribological properties than in case of the lubrication with surface-inactive lubricant. The resulting effect is related to the self-organization of friction surface. After deposition and wear resistance tests, the friction surface microstructure was analysed, as well as the surface and depth distribution of the elements.

TiAlN based wear resistant coatings modified by molybdenum addition

TiAlN based coatings have been deposited by reactive vacuum arc evaporation combined with co-deposition of molybdenum from planar magnetron source. Obtained quasi-multilayer TiAlN/(TiAl)1−xMoxN structure was affected by the specific deposition system geometry. An average molybdenum content was up to 8 at.%. The molybdenum addition resulted in a significant improvement of tribological properties manifesting itself in lowering of friction coefficient vs steel from 0.8 down to 0.5 and wear rate below 10−15 m3/Nm. Other mechanical properties like hardness and adhesion remained unaffected or slightly improved. Observed change of tribological response for studied coatings was interpreted as being caused by beneficial contribution of lubricating molybdenum oxides generated in the tribo-contact during friction process. Molybdenum addition also affected corrosion resistance. It resulted in an improved resistance to pitting corrosion accompanied by increase of corrosion potential for coatings tested by the potentiodynamic method in 0.5 M NaCl solution.

Tribological performance of TiN coatings deposited on 304 L stainless steel used for olive-oil extraction

Titanium-nitride (TiN) coatings have been developed and used by industry in numerous tribological applications, including machining, manufacturing and transportation. However, they have not attracted any attention as a tribological coating to be used in olive-oil extraction devices. In fact, since the separation of vegetation water and solid phase of the olive is always made in a continuous process and in very short time, the wear damage of the metallic devices used in this process is still a serious problem. The purpose of this study is to investigate the mechanical and tribological behaviors of TiN coating under a wide range of deposition conditions. The results of this study have confirmed that the coatings deposited using direct current (DC) bias present several distinct changes compared to those produced with pulse bias, depending on the magnitude of the duty cycle applied with and without Argon gas. Besides, different grain orientations have been detected for both kinds of TiN coatings. Tribological performances for the obtained TiN coatings were investigated using different configurations namely reciprocating sliding and pin-on-disk tests. The responses of these coatings in terms of friction coefficient and wear depth were discussed. The main results when sliding against olive seed and alumina ball as counterbody have clearly revealed a significant improvement of tribological properties with the application of DC and pulse bias voltage. Moreover, the tribological behavior of TiN did not change much with the addition of Ar gas.

Preparation of the electroless Ni–P and Ni–Cu–P coatings on engine cylinder and their tribological behaviors under bio-oil lubricated conditions

Two electroless Ni–P and Ni–Cu–P coatings on engine cylinder were prepared with chemical plating nickel technology. The coatings were characterized by Energy Dispersive X-ray spectrometer (EDX), Scanning Electron Microscope (SEM) and X-ray Diffraction (XRD). The friction and wear behaviors of cylinders with these two coatings were compared with those of the cylinder without coating under bio-oil lubricated conditions. It was found that the cylinders after coating had significant improvement of tribological properties; in addition, the Ni–Cu–P coating had higher wear resistance and lower friction coefficient than those of Ni–P coating. Under the bio-oil lubricated conditions, the evolution of friction coefficient with sliding speed agreed with the classical Stribeck curves, namely, there was a transition from boundary lubrication (BL) to mixed lubrication (ML) to hydrodynamic lubrication (HL) as sliding speed increased. The lower friction coefficient in ML regimes than that in BL regimes depended on both of the adsorbed oil film and the tribo-film on the worn surfaces. The better tribological performances of Ni–Cu–P coating than those of Ni–P coating were ascribed to the formation of a tribo-film with CuO. Therefore, the Ni–Cu–P coating showed a very potential for preventing engine cylinders from the corrosiveness of bio-oil.