共查询到17条相似文献,搜索用时 0 毫秒
1.
The mechanism of ploughing wear of martensite nodular cast iron has been investigated by means of elastic contact theory, stress interferometry, and scanning electron microscopy. Stress distributions in the contact area are plotted through numerical quadrature. The results show that the formation of cracks is between 0.2a and 0.5a (a is the radius of the contact curve). The driving force to produce crack extension along the Y axis is τ yzmax and the extension direction is 45° to the horizontal. The driving force to produce crack extension along the X axis is either τ x or τ xzmax and the direction of crack extension is 37° to the horizontal. 相似文献
2.
The effects of sliding velocity, heat-treatment and graphite shape on sliding wear of graphite crystallized chromium white cast iron were studied. Two types of graphite crystallized chromium white cast irons having flaky or spheroidal and another type of 2.6C–15Cr white cast iron were prepared for this study. The effect of sliding velocity on wear resistance was studied by the Okoshi type and pin-on-disk type wear tests on materials which have experienced “as cast” and “heat-treated” conditions. The Okoshi type wear test results are divided into two relationships depending on sliding velocity or distance. Two regimes, initial wear and steady-state wear, existed for wear loss and sliding distance. A characteristic form of wear curve with a peak and a minimum was obtained when correlating wear loss and sliding velocity. The wear resistance of graphite crystallized chromium white cast irons were superior to that of 2.6C–15Cr white cast iron. In the results of pin-on-disk tests, there was no clear difference in the reported wear loss and friction coefficient among the alloys. However, an opposite tendency has appeared in the wear loss and friction coefficient: the wear loss value reached a peak in the wear curve at 0.52 m/s, while the friction coefficient reached a minimum at 0.52 m/s. 相似文献
3.
The effect of carbide volume fraction from 13 to 41% on the wear resistance of high chromium cast irons was evaluated by means of ball mill testing. Martensitic, pearlitic and austenitic matrices were evaluated. The 50-mm diameter balls were tested simultaneously in a 40 cm diameter ball mill. Hematite, phosphate rock and quartz sand were wet ground. The tests were conducted for 200 h. Quartz sand caused the highest wear rates, ranging from 6.5 to 8.6 μm/h for the martensitic balls, while the wear rates observed for the phosphate rock ranged from 1.4 to 2.9 μm/h. Increasing the carbide volume fraction resulted in decreased wear rates for the softer abrasives. The almost complete protection of the matrix by carbides in eutectic microstructures caused the eutectic alloy to present the best performance against hematite or phosphate rock. The opposite effect was observed for the quartz sand. The quartz abrasive rapidly wears out the matrix, continuously exposing and breaking carbide branches. A martensitic steel presented the best performance against the quartz abrasive. With phosphate rock, the wear rate of 30% carbide cast irons increased from 1.46 to 2.84 and to 6.39 μm/h as the matrix changed, respectively, from martensitic to austenitic and to pearlitic. Wear profiles of worn balls showed that non-martensitic balls presented deep subsurface carbide cracking, due to matrix deformation. Similar behavior was observed in the tests with the other abrasives. In pin-on-disc tests, austenitic samples performed better than the martensitic ones. This result shows that pin tests in the presence of retained austenite can be misleading. 相似文献
4.
When a machine is in operation, two moving surfaces interact to generate a large amount of wear particles. The wear debris generated inside the machine or contaminants from outside plays important roles in both two-body and three-body wear. For all mining and port machinery, their lubricants are very likely to be polluted by contaminants such as silica and other metallic debris such as iron and nickel. In order to seek a deeper understanding of the effects of different contaminants on wear process, this project investigated sliding wear processes when silica powder and iron powder exist in lubricants.Four sliding wear tests were conducted on a pin-on-disc tester with and without the contaminants. Visual inspection, ferrography analysis, particle quantity analysis using a particle analyzer, and numerical surface analysis using confocal laser scanning microscopy (CLSM) were conducted to study the wear particles and wear surfaces. Supported by the data generated from the comprehensive analyses on the wear particles and wear surfaces, the investigation of the effects of the added contaminants to the wear processes and wear mechanisms have been carried out and presented in this paper. 相似文献
5.
The tribological behavior of ceramic Al 2O 3 coupled with gray cast iron (PHT) with different lubricants was investigated using a ring-on-block wear tester. In the wear test, air, distilled water, emulsion and oil were used as lubricants respectively in order to check the lubricating effectiveness of lubricants and the friction mechanism of solid graphite in the cast iron. Wear testing of 0.8% C steel (T8) sliding with Al 2O 3 was also carried out to compare with the test using gray cast iron. From these data the tribological behavior of graphite in the iron can be evaluated. The results show that the friction and wear of tested couples are decreased using different lubricants in the following order: air, distilled water, emulsion and oil. When lubricating with air and water, graphite in the iron as solid lubricant can decrease the friction and wear of the couples. However, when lubricating with emulsion and oil, graphite does not show the advantage of decreasing friction and wear. 相似文献
6.
The effect of a continuous phosphide network in matrices of pearlite, ferrite, martensite, and tempered martensite has been investigated on the dry wear of a grey iron, sliding at a speed of 1.5 m s −1 with stresses of 0.5 and 2.0 MPa against cast iron. A running-in period was observed with a 0.2% P iron, whereas no running-in was observed with the 1.0% P irons. The presence of a continuous phosphide network reduced the wear rate of the pearlite iron by a factor of 0.25. In the weaker matrices (pearlite, ferrite, and tempered martensite) the phosphide network stiffened the matrix, fractured, and formed a particulate composite of phosphide in the deformed surface which resisted deformation. The wear rates and wear mechanisms of the irons are presented and discussed. 相似文献
7.
This investigation pertains to the influence of some test parameters like applied load, sliding speed and test environment on the sliding wear behaviour of a grey cast iron. Properties studied were wear rate, frictional heating and friction coefficient in dry and oil lubricated conditions. The wear response of the samples has been discussed in terms of specific characteristics like load bearing, lubricating and cracking tendency of different microconstituents of the cast iron. Examination of wear surfaces, subsurface regions and debris particles has also been carried out to understand the operating wear mechanisms and further substantiate the observed response of the samples. 相似文献
8.
This paper presents comparison of wear of regular mouldboard plough shares and two plough shares made of different basic materials, steel EN 10027 (HF-1) and EN 50Mn7 (HF-2), hardfaced by a combination of two welding processes, namely shielded metal arc welding (SMAW) and high-frequency induction welding (HFIW). Wear was determined by measurements of the changes of dimensions and weight during ploughing of sandy clay soil in Croatia. The dimensions and weight losses were lower for both types of hardfaced plough shares in comparison to regular shares, and lower fuel consumption and a higher rate of work were achieved with hardfaced plough shares. Hardfaced plough shares also offer lower production costs in comparison to regular plough shares. According to the overall results, this protection method can be recommended as an efficient solution for plough share wear protection. 相似文献
9.
The wear of grey cast iron in dry sliding conditions has been studied with the aims of (1) finding the influence of working conditions on the wear rate, and (2) determining the region of speed and load where low wear is accomplished. Grey cast iron with flake and nodular graphite was submitted to investigation using a pin-on-disc machine. The results indicate that the flake graphite cast iron is more suitable for applications at speeds greater than 4 m s −1 and lower loads, while nodular cast iron has greater wear resistance at lower speeds in the range of loads investigated - from 50 N cm −2 to 200 N cm −2 相似文献
10.
This study pertains to the observations made during the sliding wear response of a zinc-based alloy in different test conditions.
The effects of sliding speed and load on the wear behaviour of the alloy have been studied. The properties evaluated were
wear rate, frictional heating and coefficient of friction. The wear performance of the zinc-based alloy has been compared
with that of a conventional cast iron in identical test conditions.
The wear rate of the samples increased with applied load and sliding speed while the seizure resistance (load) deteriorated
with speed. The zinc-based alloy exhibited less wear rate and reduced frictional heating than that of the cast iron while
friction coefficient followed a reverse trend. Observed wear response of the samples has been discussed in terms of specific
features like lubricating, load carrying, microcracking and thermal stability of various microconstituents of the samples,
and substantiated further through the features of wear surfaces, subsurface regions and debris. 相似文献
11.
Friction and wear tests of Si 3N 4 against cast iron were carried out using a ring-on-block tester lubricated by emulsion. To provide a comparison with emulsion, distilled water was also used as a lubricant in the tests. The results show that emulsion can prevent the formation of an SiO 2·2H 2O film on the iron surface. Although the friction coefficient of Si 3N 4/ iron pairs in emulsion is much greater than in distilled water, the wear of Si 3N 4 in emulsion is less. 相似文献
12.
Recent results of tribological properties of carbon nitride (CN x) coatings are reviewed. CN x coatings of 100 nm thickness were formed on Si-wafer and Si 3N 4 disks by the ion beam mixing method. Friction and wear tests were carried out against Si 3N 4 balls in the environments of vacuum, Ar, N 2, CO 2, O 2 or air by a ball-on-disk tribo-tester in the load range of 80-750 mN and in the velocity range of 4-400 mm/s.It was found that friction coefficient μ is high ( μ=0.2-0.4) in air and O 2, and low ( μ=0.01-0.1) in N 2, CO 2 and vacuum. The lowest friction coefficient ( μ<0.01) was obtained in N 2. It was also found that N 2 gas blown to the sliding surfaces in air effectively reduced the friction coefficient down to μ≈0.017. Wear rate of CN x coatings varied in the range 10 −9-10 −5 mm 3/N m depending on the environment.The wear mechanisms of CN x in the nanometer scale were studied by abrasive sliding of an AFM diamond pin in air. It was confirmed that the major wear mechanism of CN x in abrasive friction was low-cycle fatigue which generated thin flaky wear particles of nanometre size. 相似文献
13.
针对高铬铸铁铸造组织粗大,强韧性差,容易开裂的问题,进行了高铬铸铁粉末激光熔覆实验,对熔覆层的显微组织和硬度等性能进行了检测与分析,研究了不同扫描速度对熔覆层显微组织和硬度的影响,分析了多道搭接区和多层堆积区熔覆层显微组织的演变规律,揭示了多层堆积横截面的硬度分布规律。研究结果表明:通过激光熔覆可以获得晶粒细化、组织致密、无裂纹与气孔等缺陷、硬度高(可达580 HV0.2)的高铬铸铁熔覆层。将该工艺应用到零件表面强化领域,将大大提高零件的性能和使用寿命。 相似文献
14.
In the present study, a cored wire of 304 L stainless steel as sheath material and NiB and WC-12Co as filler materials was
designed and deposited to produce a new wear resistant coating containing amorphous phase by arc spraying. The microstructure
of the coating was investigated. The porosity and hardness of the coating were determined. The wear performance of the coating
was evaluated. The XRD and TEM analyses showed that there are high volume of amorphous phase and very fine crystalline grains
in the coating. DTA measurements revealed that the crystallization of the amorphous phase occurred at 579.2°C. Because metallurgical
processes for single droplets were non-homogenous during spraying, the lamellae in the coating have different hardness values,
which lie between about 700 and 1250 HV 100 g. The abrasive wear test showed that the new Fe-based coating was very wear resistant. 相似文献
15.
This study pertains to the examination of sliding wear behaviour of a gray cast iron over a range of sliding speeds and applied pressures in dry and (oil and oil plus graphite) lubricated conditions. Wear properties characterized were wear rate and frictional heating. The cast iron revealed various forms and sizes of graphite particles in a matrix of pearlite and limited quantity of free ferrite. Different solidification patterns, as controlled by the chemical composition and/or carbon equivalent of the alloy and rate of cooling, were thought to be responsible for the varying morphology of the graphite phase formed in the material matrix. Occasional decohesion of graphite at ferrite/graphite interfacial regions was also observed.The wear rate of the cast iron increased with the speed and pressure of sliding due to increasing severity of wear condition. The specimens tended to lose proper contact with the disc at larger pressures when slid dry. This was attributed to severe cracking tendency of the material. On the contrary, specimen seizure was noticed in the oil and oil plus graphite lubricated conditions; the seizure resistance (pressure) decreased with sliding speed in presence of the lubricants. The wear rate versus pressure plots attained different slopes, i.e. the rate of increase in wear rate with pressure, depending on the test environment. One slope and inappreciable effect of pressure on wear rate were noticed due to substantial cracking tendency of the cast iron when tested in dry condition. In the oil lubricated condition also, virtually one slope was observed but it was higher than that in dry condition indicating greater sensitivity of wear rate towards the applied pressure. Also, the samples attained lower wear rate in oil than in dry condition in view of suppressed cracking tendency causing more stable lubricating film formation in presence of the oil lubricant. Addition of graphite particles to the oil lubricant caused a further reduction in wear rate because of the enhanced possibility of a more stable lubricant film formation due to smearing of the graphite particles. In this case, the slope of the wear rate versus pressure plots was the least in the intermediate range of pressures irrespective of the sliding speed owing to more stable lubricating film formation.A higher rate of temperature increase with test duration (intermediate sliding distance) in the beginning was attributed to the abrasive action of the hard debris generated through the fragmentation of the initially contacting asperities. A subsequently observed lower rate of increase at longer durations could be owing to the occurrence of mild wear condition in view of less stressing of the contacting asperities and increased stability of the lubricant film formed. Increase in the rate of frictional heating at still longer durations resulted from destabilization of the lubricating film.Frictional heating increased with applied pressure and sliding speed in view of increasing severity of wear condition. The rate of increase in frictional heating was low initially up to a specific pressure followed by a higher rate of increase at still larger pressures when the tests were conducted in oil plus graphite at both the sliding speeds and in the oil lubricant at the lower speed. A constant (high) rate of increase in frictional heating with pressure was noticed in the dry condition at both the sliding speeds and in the oil lubricant at the higher speed. Low rate of frictional heating with pressure was attributed to the occurrence of mild wear condition while a higher rate of frictional heating with pressure resulted from the occurrence of severe wear condition. As far as the influence of test environment on frictional heating is concerned, least frictional heat was generated in the oil plus graphite lubricant mixture while the maximum was noticed in dry condition, intermediate response of the samples being observed in oil. Formation of more stable lubricating film was thought to be responsible for lower frictional heating in the lubricated conditions; the presence of graphite in the oil lubricant increased the extent of lubricating film formation and stability of the film so formed.The wear response of the samples has been explained in terms of cracking tendency and lubricating effects of graphite, predominance of the counteracting effects of the two parameters over each other, and lubricating film formation by the external oil (plus graphite) lubricant on the sliding surfaces in specific test conditions. Characterization of wear surfaces, subsurface regions and debris particles of the material enabled to further substantiate the observed wear performance of the samples. 相似文献
16.
介绍了由PLC作为下位机的燃气轮机进气冷却测控系统,详细阐述了测控系统的设计方案以及PLC的功能实现.运行结果表明,该系统性能稳定可靠,自动化程度高,能够满足进气冷却的测控要求. 相似文献
17.
Electron energy-loss spectroscopy (EELS) and elemental imaging under the energy-filtered transmission electron microscope are powerful tools for the characterization of iron-rich particles present in natural waters. Features present in EEL spectra (Fe-M 2,3 Fe-L 2,3 and O-K ionization edges) of goethite (α-FeOOH) have been studied with an energy filter operated at 80 keV to determine optimal quantification and elemental imaging of Fe-rich natural aquatic particles in the 30–200 nm range of thickness. For quantitative aims, the Fe-M 2,3 ionization edge cannot be used easily, but the Fe-L 2,3 edge provides more accurate results owing to a better background extrapolation. The partial cross-section of the Fe(III) M shell has been determined for iron oxide. The use of two-windows (jump-ratio) and three-windows (background stripping) imaging methods is discussed in relation to the specimen thickness. 相似文献
|