Friction and wear studies on nylon‐6/SiO2 nanocomposites

Composites of nanometer‐sized silica (SiO₂) filler incorporated in nylon‐6 polymer were prepared by compression molding. Their friction and wear properties were investigated on a pin on disk tribometer by running a flat pin of steel against a composite disc. The morphologies of the composites as well as of the wear track were observed by scanning electron microscopy (SEM). The addition of 2 wt % SiO₂ resulted in a friction reduction (μ) from 0.5 to 0.18 when compared with neat nylon‐6. This low silica loading led to a reduction in wear rate by a factor of 140, whereas the influence of higher silica loadings was less pronounced. The smooth morphology obtained after the wear test indicated the negligible contribution to friction of the pin to the nanocomposite. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1855–1862, 2004     

Infrared and ultraviolet–visible spectroscopy study of the degradation of polyester and polyester/ethylene methyl acrylate copolymer blend coatings on steel

Thermally sprayed polymer coatings have been used as protection against corrosion and wear. The aim of this study was to produce coated steel with a blend film with low‐velocity combustion thermal spraying and a fusion technique and to evaluate its chemical degradation with infrared and ultraviolet–visible spectroscopy. The substrate used was carbon steel coated with recycled poly(ethylene terephthalate) (PET), an ethylene/methacrylic acid copolymer (EMAA), or PET–EMAA blends. The degradation of the material was evaluated with an ultraviolet condensation–weathering test and a salt‐spray test. Measurements of hardness and adhesion were carried out. The tribological properties of the polymeric films were evaluated with a pin‐on‐disc test. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Corrosion and wear behavior of alumina‐polyester nanocomposite coatings

The corrosion and wear behavior of powder coatings fabricated by the electrostatic method was investigated in this study. Pure polyester coating and fabricated nanocomposite powder coating with 10 and 20 mass.% alumina nanoparticles were coated with electrostatic spraying method on the surfaces of carbon steel substrate. Coatings were cured in two regimes by oven and microwave for the appropriate time. The effects of alumina nanoparticles on the corrosion resistance of coated samples were studied by immersion and electrochemical impedance spectroscopy (EIS) tests. Also, pin‐on‐disk test was applied to evaluate the wear properties and coefficient of friction (COF) of the coatings. The results of the corrosion test reveal that the samples with 10 mass.% alumina show the best corrosion resistance and cause a reduction in corrosion rates which is about 36 times to that of the pure sample. The wear rate of nanocomposite coatings is 10 times lower than that of pure ones and also the coefficient of friction of nanocomposite samples is almost half of the pure samples. Furthermore, the nanocomposite coatings cured in the microwave show better protection properties and wear resistance than that of ones cured in an oven. POLYM. ENG. SCI., 57:846–856, 2017. © 2016 Society of Plastics Engineers     

Wear behavior of carbon fiber‐reinforced poly(phenylene sulfide)

On a pin‐on‐disc test rig, online measurements of the wear and friction of steel sliding against carbon fiber‐reinforced polyphenylene sulfide were done. Instead of the standard set‐up, a rotating composite disc and steel pin are used. The frictional behavior of this material pair results in a friction coefficient of 0.33, while a carbide film is formed in the wear track. This results in the lowering of the frictional behavior. The wear rate is rather low, but when the wear track is covered with a carbide film, suddenly the wear rate raises. This is not due to the wear of the composite material but only as a result of the start of terrible wear of the steel counter face. Moreover, the wear of the pin is strongly related to the wear track. The pin is flattened at the sides of the formed wear track, but in contact with the carbide film there is less wear, resulting in a pin with two flat sides, making contact with the original surface, and a rig in the middle of the pin following the roundness of the wear track. The frictional behavior is strongly dependent on the weft‐warp direction. POLYM. COMPOS., 27:92–98, 2006. © 2005 Society of Plastics Engineers     

Mechanical and erosion properties of CaCO3‐EMAA thermal sprayed coatings

Polymer‐ceramic composite coatings manufactured from calcium carbonate and ethylene‐methacrylic acid copolymer (EMAA) were prepared via a thermal spray process employing different CaCO₃ filler sizes (average size of 2.8, 9 or 36 μm) and loading levels from about 2.5 to 7 wt%. The optimum filler feeding characteristics, deposition efficiency and deposition rate were obtained with a 36 μm sized CaCO₃. Tensile properties, peel strength, and the erosion resistance of a pure EMAA and CaCO₃‐EMAA composite coatings were investigated. It was found that the tensile strain at fracture of the composite coating decreased with the addition of filler to a greater degree than that observed in compression‐molded polymer composites. This is attributed to an inhomogenous distribution of the filler, with more being concentrated at the boundaries of the deposited polymer particles, thereby establishing a rigid framework within the coating. Only a small filler content is necessary to establish large changes in the mechanical properties of the coating. The peel strength of a composite coating decreases with filler content, both on a mild steel substrate and a previously sprayed polymer coating. Bonding to the latter is significantly higher and offers a possibility as a bonding layer between substrates and composite coatings. The coefficient of friction is lowered with the addition of a filler. Erosion testing has shown that the erosion resistance of PF111 is little improved overall with filler addition, although some increase is found for filler contents less than 5 vol%. Polym. Eng. Sci. 44:1448–1459, 2004. © 2004 Society of Plastics Engineers.     

Wear behavior of BCS glass ceramic coating on stainless still slab

The present study aims to assess the friction and wear characteristics of BSC glass-ceramic on 304L stainless steel, fabricated by air spray method.The dry sliding friction and wear behavior were investigated using a 4?mm diameter AISI52100 steel pin on disk geometry under 3–39?N loads, at different sliding speeds in dry conditions.Average friction coefficients (COF)and wear rates were varied in the range between 0.6–0.8 and 26?×?10^?2–0.001?mm³/N?m respectively. The results show that, the frictional behavior of glass-ceramic-metal couples depended on the metal transferred from the steel pin to the glass-ceramic's surface and the applied loads. It was found that the running–in period of G39 last shorter than the G3 one, also in the case of G39 the steady state friction coefficient was lower than G3.The wear tracks were examined using scanning electron microscope, it was revealed that, the intrinsic porosity of coat has affected on the amounts of debris as an important factor for the COF values.     

Potassium sodium niobate (KNN)‐based lead‐free piezoelectric ceramic coatings on steel structure by thermal spray method

For the first time, potassium sodium niobate (KNN)‐based lead‐free piezoelectric ceramic coating with strong piezoelectric response was fabricated on stainless steel substrates by thermal spray process, after introducing NiCrAlY and yttria‐stabilized zirconia (YSZ) intermediate layers. A large effective piezoelectric coefficient (d₃₃) of 125 pm/V was obtained with the thermal‐sprayed KNN‐based ceramic coating on the steel substrates. The mechanisms of improving the structure and enhancing the properties of the KNN‐based piezoelectric ceramic coatings by introducing the intermediate layers were analyzed. Ultrasonic transducers were designed and fabricated from the KNN‐based coatings directly formed on a steel plate structure, and the feasibility for generation and detection of ultrasonic waves for structural health monitoring using the thermal‐sprayed lead‐free piezoelectric ceramic coating was demonstrated.     

Effect of the temperature on the friction‐wear properties of poly(ether ketone) with a cardo group

We studied the effect of temperature on the friction‐wear properties of poly(ether ketone) with a cardo group (PEK‐C) with a XuanWu‐3 pin‐disc friction‐and‐wear tester. Testing conditions such as the temperature obviously affected the friction and wear behavior of PEK‐C. As the ambient temperature increased, the wear of PEK‐C increased, and there was a maximum value of the friction coefficient of PEK‐C at a certain temperature. This phenomenon could be attributed to the effect of an adhesive–elastic property of PEK‐C. Scanning electron microscopy revealed that the size and shape of the wear debris of PEK‐C varied as the temperature varied. The main mechanism behind the different tribological characteristics lay in the variations of the physical state on the friction surface of PEK‐C due to the increasing surface temperature of PEK‐C. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 696–699, 2004     

SiAlON–epoxy nanocomposite coatings: Corrosion and wear behavior

In this study, epoxy powder as a matrix was combined with different contents of silicon–aluminum–oxygen–nitrogen (SiAlON) nanoparticles using a planetary ball mill. Pure epoxy and nanocomposite powders were applied on the surface of plain carbon steel components by the electrostatic spraying method. Curing of the coatings was done in an oven or microwave for the appropriate time. The coating structure and morphology of the SiAlON nanoparticles were studied by scanning electron microscopy and transmission electron microscopy, respectively. The corrosion properties of the coatings were assessed by immersion, Tafel polarization, and electrochemical impedance spectroscopy tests in 3.5% NaCl solution. The results show that addition of 10 wt % SiAlON nanoparticles markedly increases the corrosion resistance of epoxy coatings. Thus, it can be inferred that the corrosion rate of these coatings is 15 to 18 times lower than that of pure epoxy samples and 8 to 11 times lower than coatings with 20 wt % SiAlON. The higher corrosion resistance of nanocomposite coatings can be attributed to the barrier properties of SiAlON nanoparticles. The tribological performance of the coatings was studied with the pin‐on‐disk test. The results of wear testing show that the samples containing 10 wt % SiAlON provide about five times more wear resistance than pure ones and about two times more than coatings with 20 wt % SiAlON. However, the coefficient of friction for nanocomposite coatings is reduced about 50% compared to the pure sample. Also, the curing process in either regime (oven or microwave) has the same effect on the corrosion and wear properties, and the coatings are completely crosslinked. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43855.     

Tribological properties of blends of melamine‐formaldehyde resin with low density polyethylene

Tribological properties of blends of melamine‐formaldehyde resin (MFR) with low density polyethylene (LDPE) containing 1, 5, 10, 20, 25 wt% MFR were investigated. We have determined sliding wear by multiple scratching along the same groove using a micro scratch tester. Instantaneous penetration depth is lowered by the MFR addition to LDPE. However, there is less viscoelastic recovery and the residual (healing) depths increase with increasing MFR concentration. Microindentation hardness increases along with the MFR content. Since MFR is only partially miscible with LDPE, MFR‐rich islands in the PE matrix offer more interfaces and so increase hardness. Friction determined with a pin‐on‐disk tribometer using silicon nitride balls as a function of MFR concentration shows a minimum. The result is explained in terms of surface morphology seen in scanning electron microscopy. At the same time, all blend friction values are lower than for neat LDPE. Wear determined in the pin‐on‐disk tribometer decreases along with the MFR concentration increase. Thus, pin‐on‐disk wear and friction show different faces of blends tribology. Blending can be used to improve tribological properties of LDPE. POLYM. ENG. SCI., 2008. © 2007 Society of Plastics Engineers     

Action of transfer film in improving friction and wear behaviors of iron‐ and copper‐filled poly(ether ether ketone) composites

The composites of poly(ether ether ketone) (PEEK) filled with micrometer‐sized Cu and Fe particles were prepared by compression molding. The friction and wear behaviors of the composites were examined on a pin‐on‐disc friction‐and‐wear tester by sliding PEEK‐based composites against tool steel at a sliding speed of 1.0 m s⁻¹ and a normal load of 19.6N. Optical microscopic analysis of the transfer film and of the worn pin surfaces and wear debris was performed to investigate the wear mechanisms of the composites. It was found that Cu and Fe used as filler considerably decreased the wear rate of PEEK. A thin, uniform, and tenacious transfer film was formed when Cu was used as the filler, and a nonuniform and thick transfer film was formed when Fe was used as the filler. The transfer film played a key role in increasing the wear resistance of the PEEK composites. Plastic deformation was dominant for wear of PEEK–Cu, while abrasion and adhesion were dominant for wear of PEEK–Fe. Because of the strong affinity between Fe as filler and its identical counterpart in the counterface tool steel surface, the adhesion between the PEEK–Fe composite surface and the counterface tool steel surface was thus severe. This contributed to the generation of a thicker transfer film for PEEK–Fe. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 179–184, 2000     

Peel‐strength behavior of bilayer thermal‐sprayed polymer coatings

We prepared various bilayer polymer coatings of ethylene methacrylic acid (EMAA) copolymer and ionomer by the thermal‐spray process under a range of preheat temperatures (PTs) to investigate their ability to be repaired. The thermal properties, crystallinity, microstructure, and interface strength of the coatings were investigated with differential scanning calorimetry, X‐ray diffraction, scanning electron microscopy, and mechanical testing. Processing parameters influenced the final morphological structure of the coatings. The crystallinity of the coatings increased with a higher final temperature, whereas the coating density decreased. The decrease in density was attributed to the appearance of bubbles, 250 μm in size, formed in the coatings during the spray process. For the monolayer coating of polymer on a metal substrate, a higher PT produced a greater contact area of the coating to the substrate. The adhesion of EMAA ionomer to steel was always lower than that of EMAA copolymer to steel. This may have been largely due to the interfacial adhesion between the polymer and steel being dominated by strong secondary bond interactions. Experimental results also indicate that the peel strength between polymers was at least twofold stronger than that between the polymer and the steel substrate for PTs greater than 100°C. The mixed bilayer coating of ionomer on copolymer produced the highest peel strength. The interface between the plastic layers was clearly visible under the scanning electron microscope at lower PTs, becoming more diffuse with an increase in PT. On the basis of these observations, the adhesion mechanism between polymers was explained by the formation of welding points. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 214–226, 2003     

Wear Properties of Alumina/Aluminum Composites with Interpenetrating Networks

The tribological behavior of an A1₂O₃/AI composite against a steel and an alumina was investigated in pin-on-disk wear tests using unlubricated conditions in air. Various composite compositions of aluminum contents ranging from 0 to 28 vol% were investigated over a variety of contact loads and sliding speeds. Wear rate and friction force were continuously monitored during testing. Following completion of the test, pin weight loss and the profile of the wear tracks were determined. Scanning electron microscopy accompanied by EDAX analysis was used to investigate the worn surfaces and the wear debris. The wear behavior of the composites with a low metal content (<15%) during sliding against steel and alumina was found to be comparable to the wear of pure alumina. Wear occurred either on the steel or apparently simultaneously on the pin and alumina disk. With higher Al contents, wear shifts to the composite, the wear rate increases abruptly and is accompanied by fracture of the A1₂O₃ matrix. Wear appears to occur in the composite when the mechanical strain in the composite, near the contact surface, as a result of frictional loads, exceeds the fracture strain of the alumina matrix.     

Characterization of wear surfaces in dry sliding of steel and alumina on hydrogenated and hydrogen-free carbon films

Hydrogenated amorphous carbon coatings were deposited by r.f. plasma and hydrogen-free carbon films in pulsed arc discharge on stainless steel substrates. The coatings were characterized and evaluated in tribological tests. Pin-on-disc tests were used over a wide range of test parameters: normal load, 5–40 N; sliding velocity, 0.1–3.0 m s⁻¹. The wear of both coatings was of the same order of magnitude (0.7 × 10⁻³−5.1 × 10⁻³ mm³). However, the wear of the counterface was one order of magnitude higher for the hydrogenfree carbon coatings. Increasing the normal load generally caused an increase in coating wear and in most cases also an increase in counterface wear. When the steel pin was sliding against the hydrogenated carbon coating with a high sliding velocity and load, a rather thick tribofilm was formed on the pin wear surface, lowering the coefficient of friction and reducing the pin wear. The tribofilm formed on the alumina pin sliding against the hydrogenated carbon film also seemed to reduce the friction coefficient but could not prevent the pin wear. A tribofilm was also formed on the pin wear surface when the hydrogen-free carbon coating was sliding against the steel and alumina pins, but the layer was not able to protect the pins. The tribofilm did, however, lower the coefficient of friction, which was rather insensitive to the different test parameters used. According to secondary ion mass spectroscopy analyses, material transfer of the pin was detected on the disc (coated) wear surfaces. The tribofilms formed on the pin wear surfaces consisted of pin material, hydrogen, oxygen, and carbon.     

Tribological Characterization of WC–Co Plasma Sprayed Coatings

Atmospheric plasma spraying of WC coatings is typically characterized by increased decarburization, with a consequent reduction of their wear resistance. Indeed, high temperature and oxidizing atmosphere promote the appearance of brittle crystalline and amorphous phases. However, by using a high helium flow rate in a process gas mixture, plasma spraying may easily be optimized by increasing the velocity of sprayed particles and by reducing the degree of WC dissolution. To this purpose, a comparative study was performed at different spray conditions. Both WC–Co powder and coating phases were characterized by X-ray difraction. Their microstructure was investigated by scanning electron microscopy. Mechanical, dry sliding friction, and wear tests were also performed. The wear resistance was highly related to both microstructural and mechanical properties. The experimental data confirmed that high-quality cermet coatings could be manufactured by using optimized Ar–He mixtures. Their enhanced hardness, toughness, and wear resistance resulted in coatings comparable to those sprayed by high velocity oxygen-fuel.     

Hot‐fillable containers containing PET/PEN copolymers and blends

Bottles and containers made of PET are not suitable for hot filling since the limiting upper‐use temperature of this polymer is about 85°C. In the present study the properties and performance of bottles made from copolymers and blends of PET containing NDC groups and manufactured by the Injection Stretch Blow Molding (ISBM) process were investigated. These compositions possess advanced properties and can be used up to 95°C. The properties of these bottles were found to depend on their composition and microstructure. The glass transition temperature, the degree of crystallinity and the induced strains that were measured by differential scanning calorimetry and differential mechanical thermal analysis are reported. It was concluded that NDC‐containing PET based copolymers and blends could be processed by a one‐stage ISBM process into containers of improved properties and hot‐filling capabilities. Polym. Eng. Sci. 44:1670–1675, 2004. © 2004 Society of Plastics Engineers.     

Simultaneous enhancement of friction and wear resistance for high-speed braking system with Cr3C2-NiCr-coated brake disk

The current steel brake disk and Cu-based powder metallurgy brake pad used in high-speed trains suffer fading coefficient of friction (COF) and excessive wear, resulting in a shorten lifetime and numerous exhausted brake disks. High-velocity oxygen fuel (HVOF) spray-prepared coatings have proven their ability to improve COF and decrease wear rate. In this article, Cr₃C₂-NiCr coating was sprayed on a steel brake disk, and a series of emergency braking tests under dry and wet conditions were performed on a subscale brake dynamometer, to comprehensively evaluate the braking performance of coated brake disk. The results showed that the coated brake disk exhibits a higher COF at 380 km/h, which effectively inhibits the COF fade compared to the steel brake disk case. The coated brake system also achieves a lower wear rate of the brake pad at 380 km/h, showing the desired high COF and low wear rate properties of the braking system. Additionally, the coated brake disk maintained surface integrity even after severe braking tests, highlighting its potential in the braking system. Based on the characterizations of wear debris and brake pads, a harder and thinner oxide friction film plays a crucial role in achieving the excellent braking performance in coated brake disk cases.     

Study on wear and friction behavior of graphite flake‐filled PTFE composites

The wear rate and coefficient of friction for graphite flake (GF)‐filled polytetrafluoroethylene (PTFE) composites were evaluated on a pin‐on‐disk wear tester under dry conditions. Scanning electron microscopy showed significant reduction in the abrasive wear of the composites. The wear rates of 5 and 10 wt % GF composites were reduced by more than 22 and 245 times, respectively, at sliding speed of 1 m/s. With increasing sliding distance from 1 to 8 km, the wear rate of pure PTFE decreased by 1.4 times whereas that of composites, it decreased up to three times. The significant decreased in wear rate and coefficient of friction might be attributed to the formation of a thin and tenacious transfer film on the counter‐surface. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Interaction of slip‐ and flame‐spray coated carbon‐bonded alumina filters with steel melts

Ceramic foam filters play an essential role in the quest for cleanliness of cast steel parts as they facilitate turbulence reduction during mold filling as well as removal of nonmetallic inclusions. A coating on these filters is able to increase their strength and filtration efficiency by improving the adhesion of inclusions to the filter strands. In this study, Al₂O₃‐C filters were coated with an alumina slip via slip and flame spraying. The phase composition and the microstructure of the coatings were investigated before and after immersion into molten steel contained in a metal casting simulator. After contact with molten steel, Al₂O₃‐C reference filter shows intense decarburization which often influence the quality of cast steel parts due to formation of gas bubbles. Slip‐sprayed alumina coatings on such a filter promote the deposition of inclusions due to formation of a vitreous alumina layer but will also cause gas bubble formation as they exhibit a high porosity. Flame‐spray coatings have low porosity and hence, prevent formation of gas bubbles. Furthermore, they showed the highest reactivity toward the steel melt and hence, are recommended for filtration of cast products with a high demand on cleanliness.     

Potassium–Sodium Niobate‐Based Lead‐Free Piezoelectric Ceramic Coatings by Thermal Spray Process

Potassium–sodium niobate (KNN)‐based piezoelectric ceramic coatings with single perovskite phase and dense morphology were obtained by thermal spray processing. The structure, morphology, and properties of the coatings deposited at different conditions were investigated, and excellent piezoelectric performance properties were demonstrated. The piezoelectric coefficient observed in the KNN‐based coatings in this study is about one order of magnitude higher than other thermal sprayed lead‐free piezoelectric coatings as reported in literature. With analyses on the differences in the characteristics between KNN and lead zirconate titanate (PZT) compositions and the reaction mechanisms of thermal spray and ceramic synthesis, the reasons for the successful formation of single‐phase perovskite structure with high crystallinity in the thermal sprayed KNN‐based coatings while not in PZT are explained.