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1.
The self-lubricating composites Ni3Al–BaF2–CaF2–Ag–Cr, which have varying fluoride contents, were fabricated by the powder metallurgy technique. The effect of fluoride content
on the mechanical and tribological properties of the composites was investigated. The results showed that an optimal fluoride
content and a balance between lubricity and mechanical strength were obtained. The Ni3Al–6.2BaF2–3.8CaF2–12.5Ag–10Cr composite showed the best friction coefficients (0.29–0.38) and wear rates (4.2 × 10−5–2.19 × 10−4 mm3 N−1 m−1) at a wide temperature range (room temperature to 800°C). Fluorides exhibited a good reduced friction performance at 400
and 600°C. However, at 800°C, the formation of BaCrO4 on the worn surface due to the tribo-chemical reaction at high temperatures provided an excellent lubricating property. 相似文献
2.
Tribological behaviors and the relevant mechanism of a highly pure polycrystalline bulk Ti3AlC2 sliding dryly against a low carbon steel disk were investigated. The tribological tests were carried out using a block-on-disk
type high-speed friction tester, at the sliding speeds of 20–60 m/s under a normal pressure of 0.8 MPa. The results showed
that the friction coefficient is as low as 0.1∼0.14 and the wear rate of Ti3AlC2 is only (2.3–2.5) × 10−6 mm3/Nm in the sliding speed range of 20–60 m/s. Such unusual friction and wear properties were confirmed to be dependant dominantly
upon the presence of a frictional oxide film consisting of amorphous Ti, Al, and Fe oxides on the friction surfaces. The oxide
film is in a fused state during the sliding friction at a fused temperature of 238–324 °C, so it takes a significant self-lubricating
effect. 相似文献
3.
Study of tribofilms formed during dry sliding of Ta2AlC/Ag or Cr2AlC/Ag composites against Ni-based superalloys and Al2O3 总被引:1,自引:0,他引:1
S. Gupta D. Filimonov V. Zaitsev T. Palanisamy T. El-Raghy M.W. Barsoum 《Wear》2009,267(9-10):1490-1500
Herein we show that dry sliding, in air, in the 25–550 °C temperature range, of the novel Ta2AlC/20 vol.% Ag and Cr2AlC/20 vol.% Ag composites against Ni-based superalloys (SAs) and alumina led to the formation of steady-state tribofilms whose thicknesses and compositions varied depending on sliding conditions. At elevated temperatures, under both isothermal and thermocyclic conditions, relatively thick (>0.5 μm) well-compacted “glaze” lubricious tribofilms were developed as a result of joint action of tribo-chemical and tribo-mechanical factors involving repeated tribo-oxidation, mixing, fracturing, sintering, etc. They were mainly composed of oxidized constituents from both counterparts (if slid vs. SA) or solely from MAX-Ag ones (vs. Al2O3) and possessed a fine multi-layered microstructure, i.e. a more oxidized thin outermost layer and a less oxidized carbide-containing thicker inner layer. During thermocycling the tribofilms adapted to 25–550 °C temperature variations and preserved their primary macro- and microstructure, hardness, good adhesion to the matrix and lubricating characteristics. Consequently, the tribological properties of MAX-Ag/SA tribocouples did not deteriorate, but slightly improved with sliding distance. A possible mechanism of tribofilm generation and their transformations at various temperatures is discussed. The effect of SA and alumina counterparts on the formation and degradation of the tribofilms are also discussed. 相似文献
4.
The Ni3Al matrix composites with addition of 10, 15, and 20 wt% BaMoO4 were fabricated by powder metallurgy technique, and the tribological behaviors were studied from room temperature to 800 °C.
It was found that BaAl2O4 formed during the fabrication process. The Ni3Al composites showed poor tribological property below 400 °C, with high friction coefficients (above 0.6) and wear rates (above
10−4 mm3/Nm). However, the composites exhibited excellent self-lubricating and anti-wear properties at higher temperatures, and the
composite with addition of 15 wt% BaMoO4 had the lowest wear rate (1.10 × 10−5 mm3/Nm) and friction coefficient (0.26). In addition, the results also indicated that BaAl2O4 for the Ni3Al composites did not exhibit lubricating property from room temperature to 800 °C. 相似文献
5.
A high-temperature ball-on-flat tribometer was used to investigate dry and oil-lubricated friction and wear of sintered Si3N4 and Si3N4/hexagonal boron nitride (H-BN) fibrous monoliths. The friction coefficients of base Si3N4 flats sliding against Si3N4 balls were in the range of 0.6–0.8 for dry and 0.03–0.15 for lubricated sliding, and the average wear rates of Si3N4 were 10–5 mm3 N–1 m–1 for dry sliding and 10–10–10–8 mm3 N –1m–1 for lubricated sliding. The friction coefficients of Si3N4 balls against composite fibrous monoliths were 0.7 for dry sliding and 0.01–0.08 for lubricated sliding. The average specific wear rates of the pairs were of the same order as those measured for the conventional Si3N4 pairs. However, the fibrous monoliths, in combination with sprayed dry boron nitride, resulted in reduction in the lubricated friction coefficients of the test pairs and significant reduction in their wear rates. The most striking result of this study was that the coefficients of friction of the Si3N4/H-BN fibrous monolith test pair were 70–80 lower than those of either roughened or polished Si3N4 when tests were performed under oil-lubricated sliding conditions over long distances (up to 5000 m). The results indicated that Si3N4/H-BN fibrous monoliths have good wear resistance and can be used to reduce friction under lubricated sliding conditions. 相似文献
6.
Whitney Hartung Antonella Rossi Seunghwan Lee Nicholas D. Spencer 《Tribology Letters》2009,34(3):201-210
We have examined the adsorption properties of poly(l-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG)—a brush-like polymer—on Si3N4 and SiC surfaces and determined its impact on the aqueous lubrication of Si3N4 and SiC at various speeds and applied loads. The addition of PLL-g-PEG in aqueous solution reduces the interfacial friction forces significantly for self-mated sliding contacts of these two
ceramics, as compared to lubrication with water or buffer solution alone. For SiC, the improved lubricating performance by
addition of PLL-g-PEG was apparent for all tested speeds (from 1.4 to 185 mm/s under 2 N load). For Si3N4, the effect was more apparent in the slow-speed regime (≤20 mm/s under 2 N load) than in the high-speed regime (>100 mm/s),
where extremely low coefficients of friction (μ ≤ 0.006) are readily achieved by aqueous buffer solution alone. It was further observed that the optimal lubricating effect
with Si3N4 is achieved when the tribopairs are first run-in in polymer-free aqueous buffer to render the sliding surfaces smooth, after
which the PLL-g-PEG copolymer is added to the buffer solution. 相似文献
7.
Adaptive Mo2N/MoS2/Ag Tribological Nanocomposite Coatings for Aerospace Applications 总被引:1,自引:0,他引:1
Samir M. Aouadi Yadab Paudel Brandon Luster Shane Stadler Punit Kohli Christopher Muratore Carl Hager Andrey A. Voevodin 《Tribology Letters》2008,29(2):95-103
Reactively sputtered Mo2N/MoS2/Ag nanocomposite coatings were deposited from three individual Mo, MoS2, and Ag targets in a nitrogen environment onto Si (111), 440C grade stainless steel, and inconel 600 substrates. The power
to the Mo target was kept constant, while power to the MoS2 and Ag targets was varied to obtain different coating compositions. The coatings consisted of Mo2N, with silver and/or sulfur additions of up to approximately 24 at%. Coating chemistry and crystal structure were evaluated
using X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), which showed the presence of tetragonal Mo2N and cubic Ag phases. The MoS2 phase was detected from XPS analysis and was likely present as an amorphous inclusion based on the absence of characteristic
XRD peaks. The tribological properties of the coatings were investigated in dry sliding at room temperature against Si3N4, 440C stainless steel, and Al2O3. Tribological testing was also conducted at 350 and 600 °C against Si3N4. The coatings and respective wear tracks were examined using scanning electron microscopy (SEM), optical microscopy, profilometry,
energy dispersive X-ray spectroscopy (EDX), and micro-Raman spectroscopy. During room temperature tests, the coefficients
of friction (CoF) were relatively high (0.5–1.0) for all coating compositions, and particularly high against Si3N4 counterfaces. During high-temperature tests, the CoF of single-phase Mo2N coatings remained high, but much lower CoFs were observed for composite coatings with both Ag and S additions. CoF values
were maintained as low as 0.1 over 10,000 cycles for samples with Ag content in excess of 16 at% and with sulfur content in
the 5–14 at% range. The chemistry and phase analysis of coating contact surfaces showed temperature-adaptive behavior with
the formation of metallic silver at 350 °C and silver molybdate compounds at 600 °C tests. These adaptive Mo2N/MoS2/Ag coatings exhibited wear rates that were two orders of magnitude lower compared to Mo2N and Mo2N/Ag coatings, hence providing a high potential for lubrication and wear prevention of high-temperature sliding contacts. 相似文献
8.
A MoS3 precursor deposited on anatase nano-TiO2 is heated at 450 °C in an H2 atmosphere to synthesize MoS2/TiO2 nano-clusters. The nano-clusters are then characterized, and their tribological properties are evaluated. MoS2 is found to be composed of layered structures with 1–10 nm thicknesses, 10–30 nm lengths, and 0.63–0.66 nm layer distances.
The MoS2 sizes in the MoS2/TiO2 nano-clusters are smaller and their layer distances are larger than those of pure nano-MoS2. The MoS2/TiO2 nano-clusters also present a lower average friction coefficient than pure nano-MoS2, but the anti-wear properties of both the nano-clusters and pure nano-MoS2 are similar. X-ray photoelectron spectroscopy indicates that nano-TiO2 and the element Mo are transferred to the friction surface from the MoS2/TiO2 nano-clusters through a tribochemical reaction. This produces a lubrication film containing TiO2, MoO3, and other chemicals. The nano-MoS2 changes in size and layer distance when combined with nano-TiO2, producing a synergistic effect. This may further be explained using a micro-cooperation model between MoS2 nano-platelets and TiO2 solid nanoparticles. 相似文献
9.
Fe3Si, Fe3Si alloys containing Cu were fabricated by arc melting followed by hot-pressing. The friction and wear behaviors of Fe3Si based alloys with and without Cu addition against Si3N4 ball in water-lubrication were investigated. The friction coefficient and the wear rates of Fe3Si based alloys decreased as the load increased. The wear rate of Fe3Si was higher than that of AISI 304. The addition of Cu can significantly improve the friction and wear properties of Fe3Si based alloys and substantially reduce the wear rates of Si3N4 ball. The wear rate of Fe3Si–10%Cu was 2.56 × 10−6 mm3 N−1 m−1 at load of 20 N and decreased to 1.64 × 10−6 mm3 N−1 m−1 at load of 90 N. The wear rate of Si3N4 ball against Fe3Si–10%Cu was 1.41 × 10−6 mm3 N−1 m−1, while the wear rate of Si3N4 ball against AISI 304 was 5.20 × 10−6 mm3 N−1 m−1 at load of 90 N. The wear mechanism was dominated by micro-ploughing. The combination of mechanical action (i.e., shear,
smear and transference of Cu) and tribochemical reaction of Si3N4 with water was responsible for the improved tribological behavior of Fe3Si alloys containing Cu under high loads. 相似文献
10.
In this present work, the in situ Al (A380)/5 wt%TiB2 composites were fabricated through salt–melt reaction using halide salts such as potassium hexafluorotitanate (K2TiF6) and potassium tetra fluoroborate (KBF4) salts as precursors. The composites were produced at four different melt temperatures (700, 750, 800, 850 °C). The formation of particle was confirmed from XRD results. The wear behaviour of Al/5 wt% TiB2 composite was investigated by varying the wear test parameters such as sliding temperature (25, 100, 150, 200 °C), applied load (10, 20, 30, 40 N), sliding velocity (0.4, 0.7, 1, 1.3 m/s). The microstructure of Al/5 wt% TiB2 composite was correlated with the wear characteristics of the composites. The wear resistance of Al/5 wt% TiB2 composite was significantly improved due to the presence of TiB2 particle in Al matrix material. The composite produced at melt temperature 800 °C showed a higher wear resistance at applied load: 10 N, sliding temperature: 25 °C and sliding velocity: 0.7 m/s. The wear mechanism for each of the tested condition was identified from the worn surfaces using scanning electron microscopy (SEM). ANOVA test was carried out to find out significant factor for the wear resistance of composite. The checking of adequacy of experimental value for the wear behaviour of composite for different testing condition was analysed by residual plots using statistical software. 相似文献
11.
A bulk Fe67B33 alloy was prepared by a self-propagating high-temperature synthesis technique that is convenient, low in cost, and capable
of being scaled up for tailoring the bulk materials. The Fe67B33 alloy is composed of dendrites with the t-Fe2B phase and eutectic matrix with the α-Fe and t-Fe2B phases. The content of the dendrite t-Fe2B is above 80 vol.%. The compressive fractured strength and Vickers microhardness are 3400 MPa and 12.4 GPa, respectively.
The tribological performance of the Fe67B33 alloy is investigated under dry sliding and water lubricant against Si3N4 ceramic ball. The wear rates of the Fe67B33 alloy are of the magnitude of 10−5 to 10−4 mm3/m under water lubricant. It is lower than that of the Fe67B33 alloy under dry sliding (10−4 mm3/m). But both the friction coefficients are almost identical. Oxide layers form in both environments via different tribochemical
mechanisms, which led to significant differences in wear behavior. 相似文献
12.
Ti3SiC2 was thermally oxidized (TO) at 1,000 °C for 10 h. An oxide scale of ca. 25 μm was composed of rutile TiO2 and Al2O3 for the outer sub-layer and mixtures of TiO2 and SiO2 for the inner sub-layer. The tribological behavior of Ti3SiC2 and TO–Ti3SiC2 sliding against Si3N4 at 25 and 600 °C was investigated. Results indicated that at both 25 and 600 °C, the oxide scale significantly improved the
tribological performance of Ti3SiC2. The wear mechanisms of Ti3SiC2 and TO–Ti3SiC2 sliding against Si3N4 at 25 and 600 °C are briefly discussed. 相似文献
13.
In present study, the effect of Al2O3 particle reinforcement on the sliding behavior of ZA-27 alloy composites was investigated. The composites with 3, 5, and
10 wt% of Al2O3 particles were produced by the compocasting procedure. Tribological properties of unreinforced alloy and composite were studied,
using block-on-disk tribometer under unlubricated sliding conditions at different specific loads and sliding speeds. The worn
surfaces of samples were examined by the scanning electron microscopy (SEM). The test results revealed that those composite
specimens exhibited significantly lower wear rate than the ZA-27 matrix alloy specimens in all combinations of applied loads
and sliding speeds. The difference in the wear resistance of composite with respect to the matrix alloy, increased with the
increase of the applied load/sliding speed and Al2O3 particle content. The highest degree of improvement of the ZA-27 alloy tribological behavior corresponded with change of
the Al2O3 particles content from 3 to 5 wt%. At low sliding speed, moderate lower wear rate of the composites over that of the matrix
alloy was noticed. This has been attributed to micro cracking tendency of the composites. Significantly reduced wear rate,
experienced by the composite over that of the matrix alloy at the higher sliding speeds and loads, could be explained due
to enhanced compatibility of matrix alloy with dispersoid phase and greater thermal stability of the composite in view of
the presence of the dispersoid. Level of wear rate of tested ZA-27/Al2O3 samples pointed to the process of mild wear, which was primarily controlled by the formation and destruction of mechanical
mixed layers (MMLs). 相似文献
14.
Fangfang Ge Congcong Jia Ke Li Peng Li Ping Zhu Tao Shao Feng Huang 《Tribology Letters》2018,66(2):70
Hardness has been popularly considered as an essential factor defining the wear resistance of hard coatings. Here, we report magnetron sputtered Cr80Si20N nanocomposite coatings, of widely varied packing densities, that exhibited identical specific wear rates, while the hardness changed over a wide range (from ~12 to ~36 GPa). All the Cr80Si20N coatings were free of extended and uninterrupted columnar boundaries, and retained low specific wear rates in the ball-on-plate sliding tests against Al2O3 counterpart with a normal load of 5 N (less than 3.0?×?10?16 m3/N m under ambient condition and less than 2.0?×?10?15 m3/N m under 3.5 wt% NaCl solution, respectively). Post examination reveals extensive interruption or termination of cracks in the wear tracks of the under-dense coatings, indicative of extrinsic toughening mechanisms by effective relief of local contact stress. Our results suggest that a critical role of toughening rather than hardening, played in enhancing the wear resistance of hard coatings, and thus would pave a way to develop highly wear-resistant coatings with a low hardness. 相似文献
15.
This article investigated the particle size effect of micro-sized SiC on the tribological behavior of SiCp-reinforced AZ91D Mg-based metal–matrix composites (MMCs). The Mg MMCs were prepared by the melt-stirring technique for wear
tests. The hardness and coefficient of friction of Mg MMCs increases as particle size of SiC particle in MMCs increases, except
for the hardness tendency at the region between particle size of 11 and 15 μm. The SiCp/AZ91D MMCs exhibit superior wear resistance under lower and moderate sliding condition. However, the effects of the SiC particle
reinforcements on wear resistance are not as conclusive under severe sliding condition, since the matrix of MMCs were softened
at elevated temperature under such a severe condition. 相似文献
16.
Patrick Y. Chiu Jennifer R. Vail Peter R. Barry Scott S. Perry Simon R. Phillpot W. Gregory Sawyer Susan B. Sinnott 《Tribology Letters》2012,45(1):79-87
Multifunctional tribological coatings rely on combinations of materials to improve properties, such as lubricity and wear
resistance. For example, some polymer composites exhibit favorable tribological performance as solid lubricants. Here, classical
molecular dynamics simulations are used to investigate the tribological behaviors of a mixed system of polyethylene (PE) sliding
over polytetrafluoroethylene (PTFE) with the results compared with the sliding of the relevant homogeneous systems. In particular,
oriented cross-linked PTFE and PE surfaces are slid in several relative sliding directions such that the surface chains are
in-registry or out-of-registry and at various applied normal loads. The simulation results quantify the ways in which the
mixed PTFE–PE system behaves differently than either of the homogeneous systems due to the lack of interlocking phases at
the interface. These findings are compared with experimental production of polyetheretherketone (PEEK)–PTFE composites that
have unusually low wear rates of 7.0 × 10−8 mm3/Nm, coupled with a steady, low friction coefficient of μ = 0.11 for over two million sliding cycles. The simulation results
explain the atomic-scale origins of the frictional properties of this composite. 相似文献
17.
Coupled Effect of Filler Content and Countersurface Roughness on PTFE Nanocomposite Wear Resistance 总被引:1,自引:0,他引:1
In tests of PTFE with 2.9% volume content alpha-phase alumina nanoparticles (40 or 80 nm) in sliding reciprocation against
polished steel, wear rates of ~10−7 mm3/Nm were measured which is four orders-of-magnitude lower than unfilled PTFE and two orders-of-magnitude lower than with microparticles
(0.5 or 20 μm) of more conventional filler size. This was similar to that previously reported in unidirectional sliding, and
did not vary greatly with stroke of reciprocation. For a microfilled PTFE, the wear rate gradually increased towards that
of unfilled PTFE as filler content was reduced, whereas nanofilled PTFE maintained relatively constant ~10−7 mm3/Nm to filler contents as low as 0.18% before reverting towards the rapid wear rate of unfilled PTFE. Lightly filled nanocomposites
depend upon low countersurface roughness to maintain such low wear rate, and with increasing roughness the wear rate was found
to transition at a critical value to a wear rate of ~10−5 mm3/Nm. Nanocomposites with higher filler contents were able to retain the low wear rates against rougher countersurfaces, as
the critical roughness at which this wear resistance was lost tended to increase with the square of the filler content. Upon
encountering extremely high countersurface roughness in the range R
a = 6–8 μm, nanocomposites at each filler content eventually increased in wear rate to ~10−4 mm3/Nm. The steel countersurface did not appear to play an important role in the extreme wear resistance of these alumina nanofilled
PTFE composites, as comparable performance was also displayed against alumina countersurfaces. 相似文献
18.
Nanotribological properties of NbSe2 are studied using an atomic friction force microscope. The friction force is measured as a function of normal load and scan
speeds ranging from 10 nm s−1 to 40 μm s−1 under two atmospheres (air and argon). At low speed, no effect of atmosphere is noticed and a linear relationship between
the friction and normal forces is observed leading to a friction coefficient close to 0.02 for both atmospheres. At high speed,
the tip/surface contact obeys the JKR theory and the tribological properties are atmosphere dependent: the shear stress measured
in air environment is three times lower than the one measured under argon atmosphere. A special attention is paid to interpret
these results through numerical data obtained from a simple athermal model based on Tomlinson approach. 相似文献
19.
Studies to explore the nature of friction, and in particular thermally activated friction in macroscopic tribology, have lead
to a series of experiments on thin coatings of molybdenum disulfide. Coatings of predominately molybdenum disulfide were selected
for these experiments; five different coatings were used: MoS2/Ni, MoS2/Ti, MoS2/Sb2O3, MoS2/C/Sb2O3, and MoS2/Au/Sb2O3. The temperatures were varied over a range from −80 °C to 180 °C. The friction coefficients tended to increase with decreasing
temperature. Activation energies were estimated to be between 2 and 10 kJ/mol from data fitting with an Arrhenius function.
Subsequent room temperature wear rate measurements of these films under dry nitrogen conditions at ambient temperature demonstrated
that the steady-state wear behavior of these coatings varied dramatically over a range of K = 7 × 10−6 to 2 × 10−8 mm3/(Nm). It was further shown that an inverse relationship between wear rate and the sensitivity of friction coefficient with
temperature exists. The highest wear-rate coatings showed nearly athermal friction behavior, while the most wear resistant
coatings showed thermally activated behavior. Finally, it is hypothesized that thermally activated behavior in macroscopic
tribology is reserved for systems with stable interfaces and ultra-low wear, and athermal behavior is characteristic to systems
experiencing gross wear. 相似文献
20.
Kyriaki Polychronopoulou Nicholaos G. Demas Peter N. Gibson Claus Rebholz Andreas A. Polycarpou 《Tribology Letters》2010,38(1):57-68
Cu–Cr–N coatings with Cu contents between 3 and 65 at.%, Cu/Cr ratios in the 0.04–4.5 range and 21–27 at.% N, synthesized
by twin electron-beam Physical Vapor Deposition at 450 °C, were investigated and compared against substoichiometric Cr–N reference
samples. The main objective of this study is to study the influence of Cu on the structure, and the subsequent effects on
the mechanical properties, room (22 °C) and high temperature (500 and 840 °C) tribological performance of Cu–Cr–N coatings.
Using X-ray photoelectron spectroscopy, glancing angle X-ray diffraction and scanning electron microscopy, in combination
with nanoindentation mechanical property measurements and laboratory-controlled ball-on-disc sliding experiments, it is shown
that Cu–Cr–N coatings with low Cu content (3 at.%) possess sufficient wear resistance for high-temperature demanding tribological
applications. The lubricious effect of oxide formation at high temperatures is also evaluated. 相似文献