Tribological properties of nickel-based self-lubricating composite at elevated temperature and counterface material selection

Solid lubricating materials are necessary for development of new generation gas turbine engines. Nickel-based self-lubricating composites with graphite and molybdenum disulfide as lubricant were prepared by powder metallurgy (P/M) method. Their tribological properties were tested by a MG-2000 high-temperature tribometer from room temperature to 600 °C. The structure of the composite was analyzed by XRD and worn surface morphologies were observed by optical microscope. The effects of counterface materials on tribological behavior of composites were investigated. It was found that chromium sulfide and tungsten carbide were formed in the composite by adding molybdenum disulfide and graphite, which were responsible for low-friction and high wear-resistance at elevated temperatures, respectively. The average friction coefficients (0.14–0.27) and wear rates (1.0–3.5 × 10⁻⁶ mm³/(N m)) were obtained for Ni–Cr–W–Fe–C–MoS₂ composite when rubbed against silicon nitride from room temperature to 600 °C due to a synergetic lubricating action of graphite and molybdenum disulfide. The optimum combination of Ni–Cr–W–Fe–C–MoS₂/Ni–Cr–W–Al–Ti–C showed lower friction than other counter pairs. The graphite played the main role of lubrication at room temperature, while sulfides were responsible for low friction at high temperature.     

Tribological properties of composite electrochemical nickel-based coatings

Composite electrochemical coatings based on nickel with colloidal graphite and graphite bisulphate as a disperse phase are obtained. The electrodeposition of the coatings in a variable potential mode is studied. It is determined that the coefficient of sliding friction for the developed coatings decreases by a factor of two in comparison with nickel coatings without the dispersed phase. It is shown that the coefficient of friction for the coatings decreases as the thickness of the electrolytic deposit rises.     

Tribological modification of metal counterface by rubber

Sulphur vulcanizates of styrene-budadiene rubber (SBR) filled with 80 phr of silica were rubbed extensively against iron Armco or magnesium alloy (AZ 31), and chemical modification of the surface layer of metals studied. Secondary Ion Mass Spectrometer (s-SIMS) spectra revealed fragments containing sulphur. Also Raman spectra, obtained with the surface focused confocal microscope, apart metal oxides, contained absorption peaks indicated on metal sulfides and sulfates. Depth of the modification, calculated from Atomic Force Microscope profiles of ion-etched samples (s-SIMS depth profiling) reached several tens of nanometers, what corresponds to several monolayers. The thickness of modified layer was higher for magnesium alloy, due to its higher electronegative character in comparison to iron.     

铜铁合金复合摩擦材料高温摩擦行为

研究高速列车用铜铁合金复合摩擦材料的高温摩擦磨损性能。在PlintTE77高温疲劳试验机上对该材料进行高温摩擦磨损性能测试 ,并对摩擦后的磨痕进行了微观组织分析     

The effect of an alumina counterface on friction reduction of CuO/3Y-TZP composite at room temperature

The friction behavior of CuO/yttria-stabilized tetragonal zirconia (3Y-TZP) composite in dry sliding against alumina at room temperature has been investigated. The results show that an alumina counterface has a crucial role on the frictional behavior when sliding against CuO/3Y-TZP composite in comparison with other counter materials. Pure 3Y-TZP shows high friction and wear under the same conditions. It is found that the friction reduction behavior is dependent on the sliding test conditions such as load and humidity. A thin aluminum-rich layer less than 200 nm thick on the contact surface during the low friction situation has been found by various analyzing techniques including interference microscopy, micro-Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microcopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The induced change of contact conditions and interfacial chemical reaction between CuO and alumina to form the phase CuAlO₂ increase the wear of alumina and accelerates the formation of an aluminum-rich surface layer. The presence of such a layer in the contact is beneficial for reducing friction. After a certain sliding distance, the coefficient of friction shifts from a low value to a high value due to a change in the dominating wear mechanism. This transition is shown to be caused by a different composition and thickness of the interfacial layer.     

LCF behavior and life prediction method of a single crystal nickel-based superalloy at high temperature

Low cycle fatigue tests were conducted on the single crystal nickel-based superalloy, DD6, with different crystallographic orientations (i.e., [001], [011], and [111]) and strain dwell types (i.e., tensile, compressive, and balanced types) at a certain high temperature. Given the material anisotropy and mean stress, both orientation factor and stress range were introduced to the Smith, Watson, and Topper (SWT) stress model to predict the fatigue life. Experimental results indicated that the fatigue properties of DD6 depend on both crystallographic orientation and loading types. The fatigue life of the tensile, compressive, and balanced strain dwell tests are shorter than those of continuous cycling tests without strain dwell because of the important creep effect. The predicted results of the proposed modified SWT stress method agree well with the experimental data.     

Effect of particle content, size and temperature on magneto-thermo-mechanical creep behavior of composite cylinders

The effects of particle content, particle size, operating temperature and magnetic field on steady-state creep behavior of thick-walled rotating cylinders made of Al-SiC composites have been investigated. Loading is composed of a uniform magnetic field in axial direction, steady-state heat conduction in radial direction and an inertia body force due to rotation. The composite creep constitutive equation has been described by Norton’s law in which the creep parameters are functions of particle size, temperature and particle content. The composite properties are radial dependent based on volume fraction of SiC reinforcement. It has been found that the minimum effective creep strain rate belongs to a composite identified by 25% SiC at the inner and 5% at the outer surfaces. Therefore this composite has been selected for the design of the cylinder. It has been concluded that increasing particle size and operating temperature significantly increases the effective creep strain rates. It has also been illustrated that magnetic field decreases the stresses and the effective creep strain rates.     

Tribological behavior of fast-carbonized PAN/phenolic-based carbon/carbon composite and method for improving same

One purpose of the present study is to evaluate the tribological behavior of a fast-carbonized (1000 °C/min) C/C composite. One other purpose of the study is to enhance the tribological performance of the composite by applying a post-treatment comprising re-impregnation of a carbonaceous additive-doped liquid precursor. The results indicate that average coefficient of friction (COF) values of non-post-treated composites prepared with three different carbonization rates (1, 100 and 1000 °C/min) are similar (0.40-0.45). The average wear rate of samples carbonized at 1000 °C/min is about twice as large as samples carbonized at 1 and 100 °C/min. Great majority of the samples demonstrate an increase in density and a decrease in porosity after the post-treatment. Pitch-group samples generally have larger changes in density and porosity than furan-group samples. After the post-treatment, all samples demonstrate decreases in both COF and specific wear rate coefficient. Pitch-group samples generally exhibit lower wear rate than furan-group samples. Samples post-treated with pitch/carbon black and pitch/mesophase pitch demonstrate the lowest wear rates among all samples tested (only half that of untreated samples carbonized at 1 °C/min), while still maintaining relatively high COF values (close to 0.4). These results indicate that an appropriate post-treatment, especially a pitch treatment, may dramatically improve the tribological performance of fast-carbonized C/C composite.     

Tribological behavior of polytetrafluoroethylene-silica composites

The effect of finely dispersed silica on the structure and mechanical and tribological characteristics of polytetrafluoroethylene-silica composites is studied. It is shown that the introduction of a small amount of filler (0.5%) results in qualitative and quantitative changes in the supermolecular structure of the polymer matrix, which entail variations in the friction coefficient and wear rate of the composites. During friction, dispersion of the filler and its accumulation in the composite’s surface occur. Within a narrow range of the filling degree, this causes a considerable rise of the abrasiveness of the composite accompanied with high wear resistance, which may be attributed to an increase in the adhesion of transfer films. The maximal wear resistance of polytetrafluoroethylene-silica composites is found when the filler is present in a small quantity, providing for a combination of high strength characteristics, low friction coefficient, and moderate abrasiveness.     

Tribological properties of composite multilayer coating

Abstract

The use of surface coatings is emerging as one of the most important approaches in reducing friction and wear in various tribological applications. Even though single layer coatings have a wide range of applications, the performance of the single layer alone may not always be adequate to meet the desired tribological property requirements. Hence, coatings consisting of multilayers to meet different property requirements in demanding applications are required. In this study, the tribological properties of a graded composite multilayer coating, with a specific layer sequence of MoS₂/Ti–MoS₂/TiBN–TiBN–TiB₂–Ti deposited on tool steel substrate, have been investigated at temperatures of 40 and 400°C respectively. The experimental results from the tests at 40°C have shown that the friction coefficient value ranges between 0·02 and 0·034. It was found that the deposition parameters influenced the friction and durability of the coatings. Higher substrate bias was found to result in higher friction, and the coating deposited at high substrate bias and low N₂ flow showed the lowest durability. The friction coefficient and durability of the coatings were found to be highly dependent on temperature. At high temperature, the friction coefficient increases almost threefold, and the durability decreases significantly.     

Tribological behavior of polycrystalline and single-crystal silicon

SEM tribometric experiments were performed with polycrystalline silicon (poly-Si) vs. poly-Si and Si(111) vs. Si(111) interfaces in moderate vacuum to 850°C, complementing similar recent experiments on Si(100) vs. Si(100). All friction data agree with a hypothesis associating the wear- and thermal desorption-induced generation and cooling-induced adsorptive passivation of dangling bonds on the sliding surfaces with high and low adhesion and friction, respectively. Strong additional evidence is given for a surface re- and deconstruction-induced, temporary reduction in high temperature friction. The wear rate of the various Si vs. Si specimens (on the order of 10^-12 m³ /(N m)) specific to the wide temperature range vacuum test regimen is about 10⁴ times higher than that of unpolished PCD films sliding against themselves under multi-GPa unit loads and similar environmental conditions. In contrast, the characteristic load-carrying capacity of the high-wearing Si, regardless of its crystal structure, was found to be only 1 MPa. The wear mechanism of the various Si crystallinities was heavily influenced by the agglomeration and plowing of the wear debris particles trapped in the contact zone.     

Tribological behavior of three novel triazine derivatives as additives in rapeseed oil

Three novel phosphorus-free triazine derivatives, referred to as ZOO, ZOS and ZDION, respectively, were synthesized. Their thermal stabilities and anticorrosive properties were investigated. Their tribological behaviors as additives in rapeseed oil were evaluated using four-ball friction and wear testers as well. The results suggest that all the synthesized compounds have good thermal stability, corrosion inhibiting ability and excellent tribological behavior. That is, ZOS has the best extreme pressure, antiwear and friction-reducing properties under a wide range of test conditions. And, ZOO generally possesses excellent load-carrying capacity and good antiwear and friction-reducing abilities. However, ZDION shows poor antiwear effectiveness in rapeseed oil, though it is capable of improving the load-carrying capacity and friction-reducing ability of the base stock under high concentration (>1.5 wt.%) and low load (<392 N). The worn surfaces of the steel balls were observed using a scanning electron microscope coupled with an energy dispersive spectrometer (SEM/EDS) and X-ray photoelectron spectroscope (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 N- and/or O-containing organic compounds, which accounts for the better tribological behaviors of the base stock containing the synthetic additives as compared with the base stock alone.     

Tribological properties of metals,metal-like compounds,and composite materials under high temperatures

The paper presents the investigation results of tribological properties of metals, metal-like compounds, and composite materials at high temperatures. The factors affecting seizure in like and unlike combinations of materials are discussed along with their adequacy for operation in high-temperature friction joints in various media.     

Tribological behaviors of composite molecular deposition films

Polyallylamine hydrochloride (PAH)/graphite oxides (GO) ultrathin film and the multilayer film of PAH incorporated with TiO₂ enwrapped by polyacrylic acid (PAA), namely PAH/PAA(TiO₂) composite film, were prepared by molecular deposition (MD) method in laboratory. Both of them were heated to change the film forming dynamic force from electrostatic force to covalent bond so as to increase the bonding strength of the films. The structure and nanotribological properties of the films were analyzed by atomic force microscope (AFM) and ultraviolet-visible (UV) spectroscopy. It was found that these films had a much smaller friction force than their substrates and the friction force was dependent on the morphology and/or hardness of the films.     

Tribological property of self-lubricating PM304 composite

PM304 composite has been prepared by high-energy ball milling and powder metallurgy. The composition of the PM304 composite is the same as that of PS304, but the microstructure is quite different. The microstructure of PM304 composite was fine and dense, the size of self-lubricating particles in the composite was very small. The tribological properties of PM304 composites against Inconel X-750 were examined in the temperature range from room temperature to 800 °C. The friction coefficient of PM304 was ranged from 0.32 to 0.41. At room temperature, brittle fracture occurred on the worn surface. With the increase of temperature up to 200 °C, a protective layer consisting of fluorides and Ag existed on the worn surface and led to a low wear rate. The wear resistance of the PM304 was superior to that of the PS304 in the temperature range from room temperature to 650 °C. The improvement in wear resistance of the PM304 was discussed in the terms of its microstructural characteristics.     

Tribological behavior of metal matrix composites

The wear and friction behavior of continuous graphite fiber reinforced metal matrix composites was investigated. Composite materials were tested against 4620 steel at 54 m s^?1 at room temperature in air without lubricant. The graphite fibers studied included rayon-, pitch- and polyacrilonitrile (PAN)-based fibers. Both high modulus and high strength PAN-based fibers were examined. The fibers were incorporated into copper- and silver-based alloys by means of a liquid metal infiltration technique. The results of this study indicate that the type of graphite fiber in the composite is the most significant factor in the wear and friction behavior of metal matrix composites. In some high modulus fiber tin-bronze composites the fiber fraction influences the wear rate but not the coefficient of friction. Neither the matrix alloy nor the composite tensile strength per se correlate with the friction and wear properties; however, there are specific trends for the various matrix alloys.     

Tribological behavior of ZnS-filled polyelectrolyte multilayers

The pristine polyelectrolyte multilayers (PEMs) were prepared by layer-by-layer deposition technique. The ZnS nanoparticles were in situ-synthesized in the pristine PEMs, and the composite was denoted as ZnS-filled PEMs. The friction and wear properties of ZnS-filled PEMs were investigated on a UMT-2 against stainless steel ball. The morphologies of the wear traces were observed by scanning electron microscope. It was found that ZnS-filled PEMs exhibit higher antiwear life than unfilled ones. This should be attributed to the ZnS nanoparticles formed in the PEMs enhancing the load-carrying capacity. Moreover, the PEMs with three reaction cycles have considerably lower friction coefficient and higher antiwear life than the PEMs with six reaction cycles, that is to say, an optimum amount of ZnS nanoparticles within PEMs can improve the tribological performance greatly.     

Tribological analysis of tip-cantilever made of SU-8, talc and PFPE composite

ABSTRACT

SU-8 polymer with talc particle (30?wt-%) and liquid perfluoropolyether (PFPE) (30?wt-%) fillers was used as a composite to fabricate conical tip-cantilever device. The composite tip demonstrated lower coefficient of friction (～0.22) when compared with a tip made of pure SU-8 (～0.65). Fluorine was detected on the wear track and the tip surface, which resulted from the transfer of PFPE from the tip to the wear track. The counterface made of pure SU-8 remained smooth and unworn when slid against the composite tip even after 1000 cycles of sliding. This composite with improved tribological and mechanical properties can be used for fabricating small component devices such as for micro-electro-mechanical systems (MEMS).     

Effect of surface laser texture on friction properties of nickel-based composite

Laser surface texturing (LST) was performed on the nickel-based composites by a Nd:YAG pulsed laser and the regular-arranged dimples with diameter of 150 μm were fabricated on their surfaces. The textured surfaces were smeared with molybdenum disulfide powder. The tribological properties of the textured and filled composites were investigated by carrying out sliding wear tests against an alumina ball as a counterface using a high temperature ball-on-disk tribometer. The tests were conducted at a sliding speed of 0.4 m/s and at normal loads ranging from 20–100 N and from room temperature to 600 °C. The friction coefficient of nickel-based composite textured and smeared with molybdenum disulfide was found to reduce from 0.18 to 0.1 at the temperature range from 200 to 400 °C. The texture with a dimple density of 7.1% was observed to prolong wear life of MoS2 film by more than four times in comparison to the texture with other dimple densities. The lubricious oxide particles stored in the dimples reduce friction coefficient at elevated temperatures and compensate for the extra lubricant owing to the degradation of MoS₂ caused by its oxidation at high temperatures.