首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
An investigation is conducted on the unexplored synergistic effects of multilayer graphene (MLG) and Ti3SiC2 in self-lubricating composites for use in high-temperature friction and wear applications. The tribological properties of TiAl matrix self-lubricating composites with different solid lubricant additions (Ti3SiC2-MLG, MLG) are investigated from room temperature to 800°C using a rotating ball-on-disk configuration. Tribological results suggest the evolution of lubrication properties of MLG and the excellent synergistic lubricating effect of MLG and Ti3SiC2 as the testing temperature changes. It can be deduced that MLG has great potential applications as a promising high-temperature solid lubricant within 400°C, and a combination of MLG and Ti3SiC2 is an effective way to achieve and maintain desired tribological properties over a wide temperature range.  相似文献   

2.
Dry sliding tribological properties of TiAl matrix self-lubricating composites (TMSC) containing Ag, Ti3SiC2, Ag and Ti3SiC2 were investigated from 25 to 800 °C under ball-on-disk test conditions against Si3N4 counterface under the same conditions of 10 N-0.234 m/s. The results indicated that the tribological properties were strongly dependent on the lubricant additives. TMSC with the addition of Ag and Ti3SiC2 (TAT) exhibited the lower friction coefficients (0.32–0.43) and less wear rates (1.23–4.13 × 10?4 mm3 N?1m?1) in the wide temperature range of 25–800 °C. The excellent tribological properties of TAT over the wide temperature range were attributed to the synergetic effect of Ag and Ti3SiC2 lubricants, silver diffusion forming a rich-silver smooth tribo-film on the frictional surface of TAT at low and moderate temperatures from 25 to 400 °C, while Ti3SiC2 oxidation reaction forming rich-oxide tribo-film on the worn surface of TAT at higher temperatures of 600 and 800 °C.  相似文献   

3.
TiAl matrix self-lubricating composites (TMC) with various weight percentages of Ti3SiC2 and MoS2 lubricants were prepared by spark plasma sintering (SPS). The dry sliding tribological behaviors of TMC against an Si3N4 ceramic ball at room temperature were investigated through the determination of friction coefficients and wear rates and the analysis of the morphologies and compositions of wear debris, worn surfaces of TMC, and the Si3N4 ceramic ball. The results indicated that TMC with 10 wt% (Ti3SiC2-MoS2) lubricants had good tribological properties due to the unique stratification subsurface microstructure of the worn surface. The friction coefficient was about 0.57, and the wear rate was 4.22 × 10?4 mm3 (Nm)?1. The main wear mechanisms of TMC with 10 wt% (Ti3SiC2-MoS2) lubricants were abrasive wear, oxidation wear, and delamination of the friction layer. However, the main wear mechanisms of TMC without Ti3SiC2 and MoS2 lubricants were abrasive wear and oxidation wear. The continuous friction layer was not formed on the worn surfaces. The self-lubricating friction layer on the frictional surface, different phase compositions and hardness, as well as density of TMC contributed to the change in the friction coefficient and wear rate.  相似文献   

4.
More durable, low-friction self-lubricating materials in modern industry are greatly needed for tribological systems. The current paper presents the tribological performance of TiAl matrix self-lubricating composites (TSC) containing MoS2, hexagonal BN and Ti3SiC2 designated as MhT against GCr15 steel counterface under several sliding speeds from 0.2 to 0.8 m s?1 and applied loads from 6 to 12 N. The results suggested that MhT played an important role in decreasing friction coefficients and wear rates. The covering percentage of transfer layers on worn surfaces varied with the changing of sliding speeds and applied loads, hence resulting in the distinct friction and wear characteristics of TSC. TSC containing 10 wt% MhT exhibited the best excellent tribological performance at 10 N–0.8 m s?1, which could be due to the formation of the best compaction and largest coverage of transfer layer on the worn surfaces.  相似文献   

5.
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   

6.
The tribological behavior of self-mated Ti3SiC2 is investigated from ambient temperature to 800?°C at a sliding speed of 0.01?m/s in air. The results show that at the temperatures lower than 300?°C, friction coefficient and wear rates are as high as 0.95 and 10?3?mm3/N?m, respectively. With the temperature increasing to 600?°C, both the friction coefficient and wear rates show consecutive decrease. At 700 and 800?°C, friction coefficient and wear rates are 0.5 and 10?6 mm3/N?m, respectively. According to the wear mechanism, the tribological behavior of Ti3SiC2 can be divided into three regimes: mechanical wear-dominated regime from ambient temperature to 300?°C characterized by pullout of grains; mixed wear regime (mechanical wear and oxidation wear) from 400 to 600?°C; and tribo-oxidation-dominated wear regime above 700?°C. The tribo-oxides on the worn surfaces involve oxides of Si and Ti. And, species transformation occurs to these two oxides with the increasing temperature. In the competition oxidation of elements Ti and Si, Si is preferably oxidized because of its high active position in the crystal structure. Additionally, plastic flow is another notable characteristic for the tribological behavior of self-mated Ti3SiC2.  相似文献   

7.
Studies have been carried out to explore the friction and wear behaviors of NiAl matrix self-lubricating composites containing graphene nanoplatelets (NG) against an Si3N4 ball from 100 to 600°C with a normal load of 10 N and a constant speed of 0.2 m/s. The results show that NG exhibits excellent tribological performance from 100 to 400°C compared to NiAl-based alloys. A possible explanation for this is that graphene nanoplatelets (GNPs) contribute to the formation of a friction layer, which could be beneficial to the low friction coefficient and lower wear rate of NG. As the temperature increases up to 500°C, the beneficial effect of GNPs on the tribological performance of NG becomes invalid due to the oxidation of GNPs, resulting in severe adhesive wear and degradation of the friction layer on the worn surface of NG. GNPs could hold great potential applications as an effective solid lubricant to promote the formation of a friction layer and prevent severe sliding wear below 400°C.  相似文献   

8.
Conventional liquid lubricants being used in today's gas turbine engines will not be able to operate effectively in the hostile bearing environments expected in future turbine engines. The expected high operating temperatures (500–800°C) mandate new and innovative lubrication schemes to achieve success. Recent studies have demonstrated that a new class of solid lubricants, the complex chalcogenides or metal ocythiomolybdates, have good potential for high temperature lubrication. This paper describes the friction, wear and rolling contact endurance of three high-temperature bearing materials using a zinc oxythiomolybdate (ZnMoO2S2) powder lubricant. Rolling contact tests were conducted using VIM-VAR M50, micromelt T15 tool steels and silicon nitride (Si3N4) at temperatures ranging from 23°C to 649°C, using a modified ball-on-rod type rolling-contact fatigue tester. Significant improvements in friction, endurance and wear were observed at all test temperatures, and with all three materials evaluated, when ZnMoO2S2 was used as a lubricant. Overall, silicon nitride exhibited the best frictional and antiwear performance. The lubricant powder exhibited the best tribological performance with T15 and M50 specimens between 177°C and 316°C. Energy Dispersive X-Ray Analysis (EDAX) of wear tracks showed the presence of iron (Fe) on the Si3N4 specimens as well as the presence of zinc (Zn) on both the T15 and the M50 specimens.  相似文献   

9.
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   

10.
In this paper, we reported the tribological behavior of Ti3AlC2 disk sliding against SiC ball from room temperature (RT) to 1,000 °C. The tribological properties are highly dependent of testing temperature. At RT, the coefficient of friction (CoF) is as low as 0.34 in the steady state, but the wear rate is relative high (4.26 × 10?4 mm3/Nm). At 200 and 400 °C, the CoF is as high as 1.21, and the wear rates are very high, about on the order of 10?3 mm3/Nm. From 600 to 1,000 °C, however, Ti3AlC2 exhibits quite low wear rate on the order of 10?6 mm3/Nm and relative moderate CoF, 0.60–0.80. The compacted continuous oxide layer at 600 °C and above might be responsible for the outstanding wear resistance.  相似文献   

11.
The solid lubricant that is coated on a flat surface is easily removed during friction. Surface texture dimples, which act as reservoirs of solid lubricant, can prolong the wear life of solid lubricant films. We textured silver-containing nickel-based alloys by a pulse laser and filled the micro-dimples with molybdenum disulfide powders. The tribological properties of the alloys were tested by rubbing against alloyed steel on a ring-on-disk tribometer at temperatures ranging from room temperature to 600°C . After laser surface texturing, the friction coefficients of the silver-containing nickel-based alloy smeared with molybdenum disulfide powders were reduced at temperatures ranging from room temperature to 400°C. With increasing dimple density, the wear life of the MoS2 film increased while the wear rate of the nickel-based alloy decreased. The wear life of the textured surface with a dimple density of 11.2% exceeded 10,000 m at room temperature. We conclude that molybdenum disulfide and its oxides stored in the micro-dimples play a role in lubrication at room temperature and high temperatures, respectively.  相似文献   

12.
An adaptive NiMoAl–Ag composite coating was deposited by high-velocity oxy fuel spraying, and its tribological properties from 20 to 800 °C under unlubricated conditions were evaluated using a CSM high-temperature tribometer. Scanning electron microscopy, X-ray diffraction and Raman spectroscopy were used to characterize the coating and corresponding wear tracks to determine the lubrication mechanisms. The results showed that the friction coefficient of the NiMoAl–Ag composite coating was around 0.3 from 20 to 600 °C and reached the lowest value of 0.09 at 800 °C. Meanwhile, wear rates of the coating were maintained on the order of 10?5 mm3/N m at the test temperatures except for 400 and 600 °C. Characterization of the NiMoAl–Ag coating revealed that silver provided lubrication below 400 °C. Ag2Mo2O7 and Ag2MoO4, which were formed through tribochemical reactions, acted as high-temperature lubricants above 400 °C. It was especially proposed that silver in a nearly molten state was effective in reducing the friction of the NiMoAl–Ag coating at 800 °C. Moreover, a comprehensive lubrication mechanism model of an NiMoAl–Ag composite coating at 800 °C was established to explain the extremely low friction coefficient and wear rate of the coating.  相似文献   

13.
The tribological behavior of self-mated Ti3SiC2 in low viscosity fluids, that is, water and ethanol, is investigated. The results show that both water and ethanol effectively reduce the friction and wear of self-mated Ti3SiC2. The friction coefficient and total wear rates of Ti3SiC2 tribo-pair are 0.82 and 2.17 × 10?2 mm3/N m under dry condition, 0.41 and 6.50 × 10?4 mm3/N m in water and 0.16 and 2.22 × 10?4 mm3/N m in ethanol. As sliding distance is prolonged from 0.5 to 22.9 km, the total wear rates of Ti3SiC2 in ethanol can be further reduced. Mechanical wear of Ti3SiC2 is partly inhibited in water and greatly inhibited in ethanol. Surface polishing of Ti3SiC2 pin and tribochemistry are the two distinct characteristics of self-mated Ti3SiC2 in ethanol. The surface film in ethanol is composed of TiO2 and SiO. Tribo-products in ethanol, that is, silica gel and titanium dioxide, are found. Polycondensation of ethanol by the catalysis of TiO2 and SiO2?x gives birth to paraffins and olefins.  相似文献   

14.
The tribological behavior of self-mated Ti3SiC2 in bath of alcohols are investigated at sliding velocity ranging from 0.005 to 0.3 m/s. The results show that the friction coefficient and wear rates of self-mated Ti3SiC2 are reduced greatly under lubrication of alcohols compared to that under dry condition. In alcohols, smooth worn surfaces of Ti3SiC2 can be obtained. The mechanical wear is inhibited and the oxidized Ti and Si species on the worn surface are TiO2 and silica gel. The friction coefficients decrease with carbon numbers and sliding velocity in the n-alcohols. The friction coefficient decrease with sliding velocity in glycol and glycerol as well. The decrease is determined by the increase of the viscosity of alcohols. In glycerol, at 0.1 m/s and 5 N, the friction coefficient of self-mated Ti3SiC2 is 0.08 which is the lowest in this paper. The lubrication regimes are calculated according to classical lubrication theory. At velocity from 0.005 to 0.3 m/s, in all of the alcohols except glycerol, the λ are below 1 which indicates that the lubrication regime is BL. While in glycerol, the lubrication regimes vary from BL to BL and EHL, then to EHL as the velocity increases.  相似文献   

15.
Adequate high-temperature lubrication between loaded surfaces in sliding contact can be one of the most challenging tribological problems confronting today's designers. In an attempt to provide a possible solution a test program was initiated to evaluate PS400, a recently patented, high-temperature solid lubricant coating. Made from nickel–molybdenum–aluminum, chrome oxide, silver, and barium fluoride–calcium fluoride, PS400 is a variant of the earlier coating, PS304, but is formulated for higher density, smoother surface texture, and greater dimensional stability. It was initially developed to minimize the start–stop wear in foil air bearings but is expected to perform well in other high-temperature applications where sliding friction and wear are a concern, such as variable inlet guide vanes and process control valve stems. To better define its operational capabilities, a series of tests was conducted to study the behavior of PS400 under reciprocating sliding contact at temperatures from 260 to 927°C. The tests were performed on stationary, uncoated cobalt-based superalloy bushings loaded against reciprocating PS400-coated shaft specimens in a flat-on-cylinder configuration at Hertz contact pressures from 14.1 to 20.1 MPa. For tests conducted below 927°C, friction coefficients ranged from 0.37 to 0.84 with wear factors on the order of 10?5 and 10?6 at the high temperatures but substantially increased at the lowest temperature. Data collected at 927°C were limited because the coating was found to be dimensionally unstable at this temperature.  相似文献   

16.
Various solid lubricant particles have been experimentally evaluated as possible additives to oils. However, information in terms of a direct comparison of their tribological properties is still missing. In this study, we have compared the tribological properties of seven different solid lubricant micro- and nanoparticles as additives in polyalphaolefin (PAO) oil: MoS2 nanotubes, MoS2 platelets (2 and 10 μm), WS2 nanotubes, WS2 fullerene-like nanoparticles, graphite platelets (20 μm) and multi-walled carbon nanotubes. The experiments were performed in the boundary lubrication regime under a contact pressure of 1 GPa (Hertz, max) using a ball-on-disc tribotester. In general, the particles significantly decreased the friction and wear compared to the base PAO oil. We found that it was the material of the particles that largely determined their tribological performance. The effect of the size of the particles was much less important, and the morphology (shape) of the particles had little or no influence. We have also investigated the effect of ultrasonication during suspension preparation on particle damage and found that the solid lubricant particles were not notably affected, except the MoS2 and WS2 nanotubes, which became somewhat shorter.  相似文献   

17.
MoS2 coatings exhibit low coefficient of friction (COF) when sliding against aluminum; however, the magnitudes of their COF show high sensitivity to environmental conditions. Ti could reduce the sensitivity of the frictional behavior of MoS2 coatings to moisture. This study examines the tribological properties of Ti containing MoS2 coating (Ti–MoS2) tested against an aluminum alloy (Al-6.5% Si) in ambient air (58% relative humidity, RH), dry oxygen, dry air and dry N2 (< 4% RH) atmospheres. The Ti–MoS2 coating exhibited similar COF values under an ambient (0.14), dry oxygen (0.15) and dry air (0.16) atmospheres. It was found that oxidation of MoS2 to MoO3 was responsible for high COF under these testing conditions as revealed by Energy-dispersive X-ray Spectroscopy (EDS) and micro-Raman spectroscopy. However, a low and stable COF of 0.07 was observed under a dry N2 condition. This work further showed that the tests performed at elevated temperatures, up to 400 °C in a dry N2 atmosphere sustained the low and stable COF of the Ti–MoS2 coatings. The sliding tests performed under a dry N2 atmosphere prevented the formation of MoO3 and as a result, the Ti–MoS2 coatings maintained low COF values. Low COF values were also attributed to the formation of MoS2 transfer layers.  相似文献   

18.
In order to improve the tribological properties of Ni-based composites, novel adaptive Ni-based composites containing multiple lubricants were prepared via a mechanical alloying and hot-press sintering technique. The phase constituents and microstructure of the composites were characterized and the tribological properties were evaluated from room temperature to 700 °C. The results showed that the Ag2MoO4 phase decomposed and new phases of Mo2C, Ag, and MoO3 formed in the sintered composites, which can be attributed to the solid state reaction of silver molybdate lubricant during the sintering process. The wear test results indicated that the Ni-based composites containing graphite and silver molybdate lubricants exhibited superior tribological properties at ambient and high temperatures. Subsequently, the Raman results demonstrated that the composition of the tribo-layers on the worn surface of the Ni-based composites was varied with increasing temperature. Combined with the wear test results, it can be proposed that the improvement of tribological properties is due to the synergistic lubricating action of silver molybdate, iron oxide, and nickel oxide. Furthermore, Raman results of the composite containing silver molybdate and silver/molybdenum trioxide lubricants revealed that the silver molybdate lubricant can reproduce easily by the direct reaction between molybdenum trioxide and silver in the agglomerate state.  相似文献   

19.
Ni-based self-lubricating composites with multiple-lubricants addition were prepared by a powder metallurgy technique, and the effect of multiple-lubricants on tribological properties was investigated from room temperature to 700?°C. The synergetic effects of graphite, MoS2, and metallic silver lubricants on the tribological characteristics of composites were analyzed. XRD analysis showed that new Cr x S y and Mo2C phase were formed in the composites containing graphite, MoS2 and metallic Ag lubricants during the sintering process. The average friction coefficients (0.69?C0.22) and wear rates (11.90?C0.09?×?10?5?mm3?N?1?m?1) were obtained when rubbing against Inconel 718 alloy from room temperature to 700?°C due to synergetic lubricating action of multiple-lubricants. A smooth lubricating was gradually generated on the worn surface, and the improving of tribological properties was attributed to the formation of lubricious glaze film on the worn surface and their partially transferred to the counterface. The graphite played the main role of lubrication at room temperature, while molybdate phase and graphite were responsible for low friction coefficients and wear rates at mid/high temperatures. The synergetic lubricating effect of molybdate (produced in the rubbing process at high temperatures) iron oxide (transfer from disk material to the pin) and remaining graphite multiple-lubricants play an important lubricating role during friction tests at a wide temperature range.  相似文献   

20.
The wear and sliding friction response of a hybrid copper metal matrix composite reinforced with 10 wt% of tin (Sn) and soft solid lubricant (1, 5, and 7 wt% of MoS2) fabricated by a powder metallurgy route was investigated. The influence of the percentages of reinforcement, load, sliding speed, and sliding distance on both the wear and friction coefficient were studied. The wear test with an experimental plan of six loads (5–30 N) and five sliding speeds (0.5–2.5 m/s) was conducted on a pin-on-disc machine to record loss in mass due to wear for two total sliding distances of 1,000 and 2,000 m. The results showed that the specific wear rate of the composites increased at room temperature with sliding distance and decreased with load. The wear resistance of the hybrid composite containing 7 wt% MoS2 was superior to that of the other composites. It was also observed that the specific wear rates of the composites decreased with the addition of MoS2. The 7 wt% MoS2 composites exhibited a very low coefficient of friction of 0.35. The hardness of the composite increased as the weight percentage of MoS2 increased. The wear and friction coefficient were mainly influenced by both the percentage of reinforcement and the load applied. Wear morphology was also studied using scanning electron microscopy and energy-dispersive X-ray analysis.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号