Sliding friction and wear behaviour of vinylester and its composites under dry and water lubricated sliding conditions

In this paper, we studied and explored the tribological performance of pure vinylester (V), glass fiber reinforced (GFR), SiC filled glass fiber reinforced vinylester composite under dry and water lubricated sliding conditions. Friction and wear tests were carried out with configuration of a pin on a rotating disc under ambient conditions. Tests were conducted at normal load 10, 30 and 50 N and under sliding speed of 1.6 m/s, 2.8 m/s and 4 m/s. The results showed that the coefficient of friction decreases with the increase in applied normal load values both under dry and water lubricated conditions. On the other hand for pure vinylester specific wear rate increases with increase in applied normal load under dry sliding condition and decreases with increase in applied normal load under water lubricated conditions. However the specific wear rate for GFR vinylester composite and SiC filled GFR vinylester composite decreases with the increase in applied normal load both under dry and water lubricated conditions. Moreover, for the range of load and speeds used in this investigation the coefficient of friction and specific wear rates using water lubricant registered lower values than that of the dry condition. The specific wear rates for pure vinylester and vinylester + 50 wt.% GFR and SiC filled GFR vinylester composite under dry and water lubricated sliding condition were in the order of 10⁻⁷ mm³ N⁻¹ mm⁻¹.     

Wear characteristics of hybrid aluminium matrix composites reinforced with graphite and silicon carbide particulates

This investigation studies the dry sliding wear behaviour of Al matrix composites reinforced with Gr and SiC particulate up to 10%, to study the effect of % reinforcement, load, sliding speed and sliding distance on stir cast Al–SiC–Gr hybrid composites, Al–Gr and Al–SiC composites. Parametric studies indicate that the wear of hybrid composites has a tendency to increase beyond% reinforcement of 7.5% as its values are 0.0242 g, 0.0228 g and 0.0234 g respectively at 3%, 7.5% and 10% reinforcement. The corresponding values are 0.0254 g, 0.0240 g and 0.0242 g in Al–Gr composites and 0.0307 g, 0.0254 g and 0.0221 g in Al–SiC composites, clearly indicating that hybrid composites exhibit better wear characteristics. Increase of speed reduces wear and increase of either load or sliding distance or both increases wear. Statistical analysis has revealed interactions among load, sliding speed and sliding distance in composites with Gr particulates.     

Effect of addition of graphite particulates on the wear behaviour in aluminium–silicon carbide–graphite composites

Aluminium matrix composites with multiple reinforcements (hybrid AMCs) are finding increased applications because of improved mechanical and tribological properties and hence are better substitutes for single reinforced composites. Few investigations have been reported on the tribological behaviour of these composites with % reinforcement above 10%. The present study focuses on the influence of addition of graphite (Gr) particulates as a second reinforcement on the tribological behaviour of aluminium matrix composites reinforced with silicon carbide (SiC) particulates. Dry sliding wear tests have been performed to study the influence of Gr particulates, load, sliding speed and sliding distance on the wear of hybrid composite specimens with combined % reinforcement of 2.5%, 5%, 7.5% and 10% with equal weight % of SiC and Gr particulates. Experiments are also conducted on composites with % reinforcement of SiC similar to hybrid composites for the sake of comparison. Parametric studies based on design of experiments (DOE) techniques indicate that the wear of hybrid composites decreases from 0.0234 g to 0.0221 g as the % reinforcement increases from 3% to 7.5%. But the wear has a tendency to increase beyond % reinforcement of 7.5% as its value is 0.0225 g at.% reinforcement of 10%. This trend is absent in case of composites reinforced with SiC alone. The values of wear of these composites are 0.0323 g, 0.0252 g and 0.0223 g, respectively, at.% reinforcement of 3%, 7.5% and 10% clearly indicating that hybrid composites exhibit better wear characteristics compared to composites reinforced with SiC alone. Load and sliding distance show a positive influence on wear implying increase of wear with increase of either load or sliding distance or both. Whereas speed shows a negative influence on wear indicating decrease of wear with increase of speed. Interactions among load, sliding speed and sliding distance are noticed in hybrid composites and this may be attributed to the addition of Gr particulates. Such interactions are not present in composite reinforced with SiC alone. Mathematical models are formulated to predict the wear of the composites.     

Effect of sliding distance on the wear and friction behavior of as cast and heat-treated Al–SiCp composites

The present investigation aims to evaluate the effect of sliding distance on the wear and friction behavior of as cast and heat-treated Al–SiCp composites using pin-on-disc wear testing machine, giving emphasis on the parameters such as wear rate and coefficient of friction as a function of sliding distance (0–5000 m) at different applied pressures of 0.2, 0.6, 1.0 and 1.4 MPa, and at a fixed sliding speed of 3.35 m/s. Characterizing the alloy and composites in terms of microstructure, X-ray diffraction analysis, microhardness and wear surface analysis. The results revealed that the heat-treated composite exhibited superior wear properties than the base alloy, while the coefficient of friction followed an opposite trend. Moreover, the wear rate of the composite is noted to be invariant to the sliding distance and increased with applied pressures. Microstructure of composite shows fairly uniform distribution of SiC particles in the metallic matrix. The hardness value of heat-treated composite increased 20–30% by addition of SiC particles to the alloy, intermetallic phases like Al₂Mg₃ and Al₂CuMg, etc., were obtained from X-ray analysis. The wear mechanism of the investigated materials was studied through worn surfaces examination of the developed wear tracks.     

Optimization of reinforcement content and sliding distance for AlSi7Mg/SiCp composites using response surface methodology

Extruded AlSi7 Mg alloy based SiC_p reinforced (AlSi7 Mg/SiC_p) composites and the matrix alloy were wear tested on a pin on disk type tester. The work was planned so that some response surface (RS) models can be used to examine the wear behaviour of composite samples. The effects of friction load, sliding distance and reinforcement content on the wear rate and weight loss of AlSi7 Mg/SiC_p composites were evaluated by using RS optimization procedure. In the applications of RS models to engineering problems, the estimated RS models usually have a maximum or a minimum point. Through this article the RS optimization procedure was employed to optimize the reinforcement content and sliding distance for the minimization of wear rate and weight loss of tested composites. During the tests, the values of reinforcement content, friction load and sliding distance were changed on the intervals (0%, 20%), (49 N, 169 N), (100 m, 1000 m), respectively. It was shown that there exists some optimum values of reinforcement content and some optimum values of sliding distance which minimize the wear rates also weight losses of tested composites for some fixed values of friction load in the experimental region. In this concern, the average value of optimum reinforcement contents and the average value of optimum sliding distances of AlSi7 Mg/SiC_p composites minimizing the wear rate were found as 13% and 595 m, respectively. Also the average value of optimum reinforcement content minimizing the weight loss was found as 13%.     

Effect of matrix alloy and influence of SiC particle on the sliding wear characteristics of aluminium alloy composites

This article presents an effect of matrix alloy and influence of SiC particle on the sliding wear characteristics of high strength aluminium alloys AA7010, AA7009 and AA2024, composites was examined under varying applied pressure and a fixed sliding speed of 3.35 m/s. The results revealed that the wear resistance of the composite was noted to be significantly higher than that of the alloy and is suppressed further due to addition of SiC particles. The overall observation among the matrix alloys, AA7010 alloy shows maximum wear resistance than that of the other, and can withstand the seizure pressure up to 2.6 MPa. The wear mechanism was studied through worn surfaces and microscopic examination of the developed wear tracks. The wear mechanism strongly dictated by the formation and stability of oxide layer, mechanically mixed layer (MML) and subsurface deformation and cracking. The overall results indicate that the high strength aluminium alloys and composite could be considered as an excellent material where high strength and wear resistance components are prime importance especially designing for structural applications in aerospace and general engineering sectors.     

Friction and wear properties of TiCN coatings sliding against SiC and steel balls in air and water

The TiCN coatings were deposited on WC cemented carbides using enhanced cathodic arc magnetron sputtering. The topography of TiCN coatings were observed using scanning electron microscopy (SEM), the composition and structure of TiCN coatings were analyzed by energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The friction and wear properties of TiCN coatings sliding against SiC and steel balls in air and water were investigated using ball-on-disk tribometer. The results showed that the TiCN coatings had a strong (111) preferred orientation. The friction coefficient and the specific wear rates of the TiCN/SiC tribopairs in air were higher than those in water. When the TiCN coatings slid against SiC balls in water, the friction coefficient and the specific wear rates first decreased, and then increased with the normal load, but decreased linearly with the sliding velocity. The lowest friction coefficient of 0.171 was obtained at 3 N and 0.4 m/s, while the lowest specific wear rate of the TiCN coatings was 2.3 × 10^− 6mm³/Nm at 6 N and 0.1 m/s. The TiCN coatings were worn out when the normal loads were higher than 6 N. When the TiCN coatings slid against the SUJ2 and SUS440C balls in water, the friction coefficient increased to 0.271 and 1.026 respectively. The EDS analysis showed that Fe and O elements existed on the wear track. This indicated that the tribochemical reaction occurred at the friction contact area.     

Three-body abrasion on wear and frictional performance of treated betelnut fibre reinforced epoxy (T-BFRE) composite

This work aims to investigate the wear and frictional behaviour of a new epoxy composite based on treated betelnut fibres subjected to three-body abrasion using different abrasive particle sizes (500 μm, 714 μm and 1430 μm) and sliding velocities (0.026–0.115 m s⁻¹) at constant applied load (5 N) using a newly developed Linear Tribo Machine. The worn surfaces of the composite were studied using scanning electron microscope. The work revealed that the predominant wear mechanism of treated betelnut fibre reinforced epoxy (T-BFRE) composite sliding against grain sands was plastic deformation, pitting and pullout of betelnut fibres. The composite exhibited higher values in frictional coefficient when it was subjected against coarse sand. Besides, the abrasive wear of the composite is depending on the size of abrasive particles and sliding velocity. Higher weight loss is noticed at high sliding velocities. The specific wear rate for the composite subjected to three different sand particles follow the order of: coarse > grain > fine sands respectively.     

Microstructures and improved wear resistance of 3D needled C/SiC composites with graphite filler

Three-dimensional (3D) needled carbon/carbon (C/C) composites with a lowest porosity of 15.6% were achieved after 1 cycle of impregnation by phenolic resin slurry containing graphite filler, hot-pressing curing and pyrolysis. Carbon/silicon carbide (C/SiC) composites were obtained by liquid silicon infiltrating C/C composites. The aim was to incorporate cost effectiveness and excellent performance of C/SiC braking material. Using filler content not exceeding 30 wt% in the slurry promised undamaged C/C segments in C/SiC composites. The linear wear rate of C/SiC using 30 wt% filler was 0.33 μm side⁻¹ cycle⁻¹ and displayed a fourfold decrease; its weight wear rate was 2.46 mg side⁻¹ cycle⁻¹ and minus 171%, compared with the previously reported values of C/SiC without filler, at a braking velocity of 28 m/s. Its friction coefficients and friction stability coefficients appeared relative insensitive to changes in braking velocities and displayed higher values at high braking velocities compared with the previous values.     

Dry sliding wear behavior of as-cast ZE41A magnesium alloy

In present work, an attempt has been made to investigate the wear behavior of as-cast ZE41A magnesium alloy during dry sliding. The experiments were performed using pin-on-disc type wear apparatus against a EN32 steel counterface in a load range of 30–150 N, sliding velocity range of 0.5–2.5 m/s and at a constant sliding distance of 1500 m. Microstructural investigations on the worn surfaces were undertaken using a scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS) for determination of type of damage and nature of distortion at the surface. Wear mechanisms such as abrasion, oxidation, delamination, plastic deformation and melting were identified. Wear maps were drawn for the test result data. Mild wear, severe wear and ultra severe wear regimes were identified using wear transition map through microstructural observations.     

Tribology of ultra high molecular weight polyethylene film on Si substrate with chromium nitride, titanium nitride and diamond like carbon as intermediate layers

This paper presents tribological studies on composite films consisting of different intermediate hard layers (chromium nitride (CrN), titanium nitride (TiN) and diamond like carbon (DLC)) on Si substrate followed by soft ultra high molecular weight polyethylene (4-5 μm thick) as the top layer. The tribological properties of the composite films were evaluated on a ball-on-disc tribometer (composite film sliding against a 4 mm diameter Si₃N₄ ball) at a normal load of 40 mN and a linear speed of 0.052 m/s. The wear durability of the composite films increases with increasing hardness of the intermediate layers. The composite film with harder intermediate layers (TiN with 24 GPa and DLC layers with 57 GPa and 70 GPa of hardness) provides the best tribological performance with more than 300,000 cycles of sliding when the experiments were stopped. The critical loads of scratching correlate with the wear performances of the composite films. Application of only a few nanometer overcoat of perfluoropolyether on the most wear resistant composite films can further increase the wear lives (more than one million cycles) even at a higher normal load of 70 mN.     

Effect of aging on the abrasive wear properties of AlMgSi1 alloy

In this paper, the wear performance of the aged AlMgSi1 alloy was investigated. Great improvements in mechanical properties of Al alloys can be achieved by suitable solution treatment and aging operations. A pin-on-disk wear machine was designed and developed for abrasive wear tests. The wear resistance was evaluated using a pin-on-disk wear testing method with a SiC abrasive paper counterface. The variation of wear volume is presented as a function of applied normal load, abrasive grit size and sliding distance for running speed. Mass losses were measured within a load range of 6.45–11 N, a sliding velocity range of 0.078–0.338 m/s and abrasive grit size of 5–30 μm. The effects of different sliding speeds and loads on wear resistance and surface roughness were also examined. It was measured amounts of mass loss and examined worn surfaces. Metal microscope was used to study the microstructures of the wear scars. Natural aged specimen observed maximum wear resistance.     

Effect of the SiC particle size on the dry sliding wear behavior of SiC and SiC–Gr-reinforced Al6061 composites

The effect of size of silicon carbide particles on the dry sliding wear properties of composites with three different sized SiC particles (19, 93, and 146 μm) has been studied. Wear behavior of Al6061/10 vol% SiC and Al6061/10 vol% SiC/5 vol% graphite composites processed by in situ powder metallurgy technique has been investigated using a pin-on-disk wear tester. The debris and wear surfaces of samples were identified using SEM. It was found that the porosity content and hardness of Al/10SiC composites decreased by 5 vol% graphite addition. The increased SiC particle size reduced the porosity, hardness, volume loss, and coefficient of friction of both types of composites. Moreover, the hybrid composites exhibited lower coefficient of friction and wear rates. The wear mechanism changed from mostly adhesive and micro-cutting in the Al/10SiC composite containing fine SiC particles to the prominently abrasive and delamination wear by increasing of SiC particle size. While the main wear mechanism for the unreinforced alloy was adhesive wear, all the hybrid composites were worn mainly by abrasion and delamination mechanisms.     

Effect of re-scanning on tribological characterization of laser surface alloyed layers

Laser surface alloying (LSA) is increasingly recognized as a powerful surface modification tool for enhancing the wear resistance of engineering components. Experimental investigations have been carried out to examine the influence of re-scanning on tribological behavior in laser surface alloying of Al with Ni. Dry sliding wear tests have been conducted using a reciprocating machine under different normal loads of 10, 15, and 20 N and at a constant sliding speed of 0.1 m/s. Re-scanning was found to substantially affect the laser-alloyed layer, including its phase constitution. Re-scanning leads to higher hardness compared to a single-time scan; however, the specific wear rate following re-scanning is lower. These observations are rationalized in terms of microstructure and the wear mechanism.     

Wear assessment of plasma nitrided AISI H11 steel

Plasma nitriding is one of the effective methods for improvement of the hardness, wear and corrosion resistance of steels. In this research AISI H11 hot working tool steel was plasma nitrided in various gas mixtures for different times and temperatures. The morphology, size and composition of nitride nanoparticles formed on the surface of the specimens were investigated using scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD). The wear behavior of plasma nitrided samples was studied by means of unlubricated pin-on-disc method under constant load of 80 N, sliding speed of 1 m/s, sliding distance of 2000 m at room temperature. The results showed plasma nitriding process improved the wear behavior of H11 steel. The increase in time and temperature of plasma nitriding decreased the hardness and increased the wear weigh loss of the specimens.     

Investigation of the abrasive wear behaviour of ZA-27 alloy and CuSn10 bronze

In this study, abrasive wear behaviours of ZA-27 alloy and CuSn10 bronze were investigated using a purpose-built wear tester. The ZA-27 alloy was produced by permanent mould casting. The abrasive SiC particles having 63 μm grit size was added to the lubricant oil. The wear rate and friction coefficient of alloys were determined at the different test conditions such as sliding distance, applied load, linear velocity and percentage SiC weight content. The wear surfaces of alloys were examined using SEM and EDS analysis. The results showed that the wear rate of alloys decreased with the increasing of applied load and increased with the increasing linear velocity and abrasive SiC content. It was found that the SiC particle fracture was an important mechanism determining the friction and the wear rate of alloys. CuSn10 bronze showed higher wear resistance than ZA-27 alloy under abrasive test conditions except at high linear velocities.     

The wear of aluminium-based journal bearing materials under lubrication

The aluminium-based alloys, nowadays, are developed to be used in high performance engine bearings. In this study, new Al-based bearing alloys, which are produced by metal mould casting, were developed; and tribologic properties of these alloys under lubrication were analyzed experimentally. Four different aluminium alloys were carried out on pin on disc wear tester for that purpose. SAE 1040 steel was used as the disc material in the wear tester. Friction tests were carried out at 0.231–1.036 N/mm² pressures and at 0.6–2.4 m/s sliding speeds. Wear tests were carried out at 1.8 m/s sliding speed and at 70 N normal load. Friction coefficients and weight losses of the samples were determined under various working conditions as a result of the experiments. The morphographies of the worn surfaces were analyzed. Hardness, surface roughness, and surface temperature of the samples were measured. The results showed that the friction and wear behaviors of the alloys have changed according to the sliding conditions. The effects of the elements except aluminium composing alloys on the tribologic properties were analyzed. Al8.5Si3.5Cu alloy has a lower friction coefficient value than other alloys. Al8.5Si3.5Cu and Al15Sn5Cu3Si alloys, on the other hand, have the highest wear resistance. Al15Pb3.7Cu1.5Si1.1Fe alloy is the most worn material; and Al15Pb3.7Cu1.5Si1.1Fe alloy has the highest wear rate. As a result of the evaluations conducted, Al–Sn and Al–Si alloys, which include Si and Sn, can be preferred, among the aluminium alloys that will work under lubrication, as the bearing material.     

Dry sliding wear behavior of cast SiC-reinforced Al MMCs

Dry sliding block-on-ring wear tests were performed on a squeeze cast A390 Al alloy, a high pressure die cast 20%SiC–Al MMC, and a newly developed as-cast 50%SiC–Al MMC. The testing conditions spanned the transition that control the mild to severe wear for all materials. The results show that the sliding wear resistance increases as SiC particle volume fraction increases. The critical transition temperature, at which wear rates transit from mild to severe, also increases with increasing SiC content. Examination of the wear surfaces, the subsurface characteristics, and the wear debris indicate that a hard ‘mechanically alloyed’ layer, high in SiC content, forms on the sliding surface of the 50%SiC composite. This layer prevents the surface adhesion wear mechanisms active in the A390 alloy, and it inhibits delamination wear mechanisms that control the mild wear of the 20%SiC composite. As a result, mild wear of the 50%SiC composite occurs by an oxidation process. In the 20%SiC material, severe wear occurs as a consequence of material removal by a flow-related extrusion-like process. In contrast, the high SiC content prevents plasticity in the 50%SiC composite, which eventually is susceptible to severe wear at very high temperatures (≈450 °C) due to a near-brittle cracking processes.     

Wear coefficient and reliability of sliding wear test procedure for high strength aluminium alloy and composite

This paper describes the results of dry sliding wear tests of aluminium alloy (Al–Zn–Mg–Cu) composite was examined under varying applied pressures (0.2–2.6 MPa) and sliding speeds of 0.52, 1.72, 3.35, 4.18 and 5.23 m/s. The wear behaviour was studied using pin-on-disc apparatus against heat-treated steel counter surface, giving emphasis on the parameters such as wear coefficient as a function of applied pressure for alloy and composite for various sliding velocities. Wear coefficient of the alloy was noted to be significantly higher than that of the composite and is suppressed further due to addition of silicon carbide particles and applied pressure. It is noted that the experimental values are in good agreement with the theoretically calculated value. The maximum deviation of experimental values from the theoretical ones is noted to be around 10–15%. This supports the reliability of the test procedures and reproducibility of the test data.     

Wear resistant coatings: Silica sol-gel reinforced with carbon nanotubes

Pin-on-disc wear experiments have been carried out on sol-gel silica coatings reinforced with 0.1 wt.% carbon nanotubes (CNTs) deposited on WE54 magnesium alloy substrates by the dip-coating technique. Sol-gel solutions were fabricated using two different procedures: mechanical mixing (MM) and ultrasonic probe mixing. Dry sliding wear tests have been carried out at load of 1 N, speed of 0.1 m/s and sliding distance of 60 m. Friction coefficients were obtained from the tests and the specific wear rates (k) were calculated. The fabrication procedure of the coating influences its morphology and wear resistance. Friction coefficient was found to vary slightly with the addition of the CNTs. The wear volume of the magnesium substrate coated decreased by 40% and 80%, in terms of k, by using unreinforced and CNT-reinforced MM coatings, respectively. In MM layers reinforced with CNT uniform dispersion of the nanotubes was reached and toughening of the ceramic coating by pull-out and crack bridging mechanisms was observed.