1045钢在部分滑移区和滑移区内的高温微动磨损性能研究

从室温到400℃，对GCr15钢与1045钢组成的摩擦副进行了微动摩擦拭验。法向载荷变化范围为100—300N、位移幅值为15—60μm。通过摩擦动力学分析，结合显微观测，发现1045钢的高温微动行为与微动区域特性密切相关。在滑移区内，随着温度的升高，摩擦系数与磨损降低，但在部分滑移区内，温度对微动行为影响很小。     

Wear Mechanisms at High Temperatures. Part 1: Wear Mechanisms of Different Fe-Based Alloys at Elevated Temperatures

To extend the lifetime of the sinter grate used to crush the sinter cake into smaller pieces for steel fabrication, a study was undertaken to investigate which wear processes are primarily responsible for limiting the lifetime of the sinter grate. Several wear processes could be identified. The sinter temperature which is up to 800 °C causes temperature-induced material ageing and oxidation. The falling of the sinter cake onto the sinter grate causes high impacts, erosion and abrasive wear. There is enormous economic pressure, which makes the most cost-efficient solution the most attractive one, not the technically “best” coating material; thus, Fe–Cr–C hardfacing alloys are mostly used. In view of the above, four different alloys which are promising for this application were studied with regard to their wear resistance. Each wear mechanism was investigated in a special test tribometer. Fatigue wear caused by multiple impacts and abrasion was tested in the high-temperature continuous impact abrasion test. Materials behaviour in heavy single impacts was evaluated in the single impact test. Characterisation of microstructure and wear behaviour was performed by optical microscopy and scanning electron microscopy. The results obtained with the help of the different measurement techniques were linked and set into comparison to calculate the volumetric wear of the specimen. Aim of this work was to investigate the influence of the material parameters such as macrohardness, hard phase content, microstructure coarseness on the wear resistance in impact loading and abrasive applications at high temperatures. Results also indicate that the matrix ability to bind carbides at high temperature as well as the matrix hardness at high temperatures strongly influence the wear resistance in the different tests. Those material parameters get correlated to the wear rates in different material demands. The test results indicate that at higher temperatures material fatigue becomes a major wear-determining factor which makes the matrix hardness and the matrix ability to bind carbides at high temperatures very important. Especially, in abrasive wear, a certain content of hard phases is also necessary to keep the wear to a lower level. It could also be shown that in impact loading applications, a coarse microstructure is a disadvantage.     

温度对受电弓滑板材料磨损的影响

在销-盘试验机上试验研究温度对受电弓滑板材料摩擦磨损的影响,探索在各种温度下弓网系统的摩擦磨损性能。试验结果发现,温度是影响弓网系统摩擦因数和磨损量的主要因素之一。干态摩擦时,摩擦因数随着试验温度的升高而增大。磨痕的SEM和EDS分析显示,温度较低的情况下,摩擦表面有大量的犁沟和磨粒,主要以磨粒磨损为主,对应的磨损量比较少。高温时,摩擦表面有氧化、熔融的特征,主要以黏着磨损为主,对应的磨损量比较大。     

Influence of Heat Treatment on Microstructure and Sliding Wear of Thermally Sprayed Fe-Based Metallic Glass Coatings

Fe₆₂Ni₃Cr₄Mo₂W₃Si₆B₁₇C₃ amorphous coatings were thermally sprayed by a high velocity oxygen fuel spraying system (DJ-2700) and heat-treated at the temperatures ranges from 873 to 1,173 K in vacuum for 1 h. Differential scanning calorimetry, X-ray diffraction (XRD), and scanning electron microscopy were used to study the microstructural characteristics of the coatings. Vickers hardness tester was used to measure the hardness of the coatings. At the same time, the sliding wear behavior of the coatings was evaluated in a reciprocating ball-on-disk system. Within the resolution of XRD, amorphous structure without apparent crystalline phases was obtained in the as-sprayed coating. The heat treatments above 873 K led to the crystallization of amorphous phase. With the increase of heat treatment temperature, diffusion and sintering could occur between the layers of the coatings. The highest microhardness was obtained in the coating heat-treated at 973 K. When wear tested at a relative low load of 2 N, a direct correlation between the hardness and wear resistance of the coatings seems to be reasonable. However, at relative high loads, the wear resistance of the coatings is dependent on the resistance to crack initiation and growth between the layers rather than the hardness.     

高能冲击磨损中白层组织对材料磨损性能的影响

利用模拟球磨机工矿条件的高能冲击磨损实验装置研究了高能冲击磨损中材料的几种磨损机制,高能冲击磨损过程中表层材料不仅由于剧烈的塑性变形和切削造成磨损,而且还因为产生了独特的表层和亚表层的白层组织,在冲击过程中易于诱发产生裂纹,从而加剧材料的磨损流失。     

The Influence of Lead Suspension in Oil Lubricant on the Sliding Wear Behaviour of Cast Iron

This investigation pertains to the analysis of the sliding wear response of a cast iron over a range of applied pressures in the presence of an oil lubricant. The effect of varying concentrations of lead particles suspended in the oil lubricant on the wear behaviour of the cast iron was also examined. The wear rate increased with pressure initially at a lower rate followed by a higher rate of increase beyond a specific pressure. Furthermore, the presence of suspended lead particles up to a specific concentration in the oil proved beneficial while the trend reversed at still higher concentrations. The extent of frictional heating increased with test duration at a high rate in the beginning of the tests. This was followed by a reduced rate of temperature increase at longer test durations. In some cases, the rate of temperature rise increased once again while it reduced in one case towards the end of the tests. The severity and extent of frictional heating also increased with pressure. Lead addition to the oil lubricant up to a specific concentration led to a reduced degree of heating while the trend reversed at still higher lead contents. Specimen seizure caused significantly high wear rate and frictional heating. The observed wear response of the samples has been explained in terms of specific characteristics like cracking tendency and lubricating and load bearing capacity of various microconstituents of the specimen material. Another important factor of concern affecting wear characteristics was observed to be lubricating film formation and its stability during sliding. The wear behaviour has also been substantiated through the characteristics of wear surfaces and subsurface regions.     

Wear Behavior of Bronze Hybrid MMCs Coatings Produced by Current Sintering on Steel Substrates

In this work, a bronze matrix (90 wt% Cu + 10 wt% Sn) was reinforced with SiC and graphite particulates using mechanical alloying and a subsequent current sintering technique. The mechanically ball-milled bronze hybrid matrix composite powders reinforced with 5.0 wt% SiC and 5.0 wt% graphite were cold-compacted on a 1040 steel substrate under a pressure of 300 MPa. The compacted structure was sintered at atmospheric conditions to nearly a full density within 10 min using current sintering, in which the powders were heated by a low voltage and high current and compressed simultaneously. The samples were sintered at three different applied currents (1,500, 1,700, and 1,900 A) to provide dense and well-bonded coatings on steel substrates. Microhardness testing and optical and scanning electron microscopes (SEM) were used for microstructural characterization of the hybrid composites. The tribological characterization of the resulting composites was tested by a block-on-disk method for determination of the wear loss and friction coefficient behaviors against a steel disk. It was pointed out that increasing applied current during the sintering/coating process resulted in obtaining high-hardness and wear-resistant hybrid composite coatings.     

Wear Mechanisms at High Temperatures: Part 2: Temperature Effect on Wear Mechanisms in the Erosion Test

In previous investigations on wear mechanisms at high temperatures made in High Temperature-Single Impact Test (HT-SIT) and High Temperature-Continuous Impact Abrasion Test (HT-CIAT), predominant wear mechanisms were identified and correlations to different material parameters could be presumed. In order to confirm these correlations, four different alloys which are promising to be used in high temperature applications like a sinter grate have been studied in the High Temperature-Erosion Test (HT-ET) by the use of different impact angles and different impact energies. Especially the change of wear mechanism caused by increasing testing temperature was analysed in detail. Characterisation of microstructure and wear behaviour has been done by optical microscopy (OM) and scanning electron microscopy (SEM). Results obtained by the use of the different measurement techniques were linked and set into comparison to calculate the volumetric wear of the specimen. Predominant wear mechanisms were determined using OM in the mode of cross-section images and SEM. The results indicate that material parameters such as hardness and hard phase content can be correlated to the erosion wear rates at different impact angles. The test results indicate that at higher temperatures, the material fatigue becomes a major wear-determining factor. The test results also confirmed that there is a critical impact energy for each material above where the wear rate increases significantly. Test results with thermally aged materials also show that a better heat-resistant matrix reduces the material fatigue thus resulting in lower wear rates.     

The Influence of Temperature on the Wear of Carbon Fiber Reinforced Resins

Wear of carbon fiber composites increases with increasing temperature. At temperatures below about 100 C, wear is influenced by the type of carbon fiber and the presence of transfer films on the counterface. Beyond 100 C, transfer films no longer exist and wear becomes independent of the type of fiber. Increasing rates of wear at elevated temperatures are attributed to progressive desorption of water from the carbon fibers.

Reduced wear at elevated temperatures may be achieved by incorporation of CdI₂ in the composite. However, volatility of this material restricts the temperature capability of composites to approximately 350 C.     

变形温度对耐候钢高温塑性的影响

在不同的变形温度(600~1250℃)下,以3×10-3s-1的应变速率对试样进行拉伸直至断裂。绘制出高温塑性曲线,分析变形温度对耐候钢高温塑性的影响。耐候钢的第Ⅲ脆性区出现在700~850℃,脆性区间温度范围较窄;900~1150℃为最佳塑性区间。     

3Cr2W8V钢高温磨损的研究

采用销盘式高温磨损试验机对3Cr2W8V钢进行高温磨损试验,研究了淬火温度对3Cr2W8V钢磨损性能的影响,采用SEM、EDS、XRD分析磨损表层成分、形貌和结构,探讨高温磨损机制.研究表明,淬火温度对3Cr2W8V钢高温磨损率有着显著影响.1 050～1 150 ℃范围淬火,磨损率较低;过低或过高温度淬火,磨损率显著升高.3Cr2W8V钢磨损表面氧化物膜下基体发生了明显的塑性变形,并在基体中出现了裂纹及氧化物.3Cr2W8V钢高温磨损机制为氧化物的疲劳剥落.     

硬质合金刀具高温磨损过程机理分析

大型加氢筒节零件采用难加工材料,在加工过程中刀具常会因为高温高压而磨损失效,严重影响刀具寿命,阻碍生产率的提高。为了研究切削温度对硬质合金刀具磨损机理的影响,设计并进行了2.25Cr-1Mo-0.25V钢切削试验,分析不同切削参数下刀具的高温磨损机理,并通过有限元仿真方法进行了验证,获得不同切削参数下切削温度对刀具磨损的影响规律,为刀具的设计开发和切削参数的优化提供了理论参考。     

高温应变时效对P92钢高温低周疲劳性能的影响

分别在应力与应变控制下对P92钢进行550℃高温低周疲劳试验,研究该钢在不同应变幅(0.2％～1.0％)和应力幅(280～350 MPa)下的疲劳行为;对P92钢进行不同预拉伸应变(0～4％)和温度(250～350℃)下的应变时效处理后,研究该钢的高温拉伸与低周疲劳性能.结果表明:在应变控制下,P92钢的应变与疲劳寿命...     

铣削方式对高速铣削TC4钛合金刀具磨损的影响

为研究高速铣削TC4钛合金时不同铣削方式对刀具磨损的影响,在铣削速度为200m/min时采用硬质合金刀具对工件分别进行顺铣、逆铣和交替铣的切削试验。分析了不同铣削方式下刀具磨损的特点和形貌,并对刀具耐用度进行了对比。结果表明:在此铣削速度下,硬质合金刀具在不同铣削方式下的磨损特征主要表现为前刀面刃口处的塌陷及后刀面的沟槽磨损。刀具耐用度在顺铣方式下较好,交替铣、逆铣时的刀具耐用度则大大低于顺铣,且交替铣比逆铣刀具耐用度稍好。     

高温下位移幅值对TC4合金磨损性能的影响

钛合金的微动磨损会加速裂纹的形成与扩展,导致其构件提前失效。利用摩擦磨损试验机考察TC4合金在300和500℃温度下的微动磨损行为,利用扫描电子显微镜和激光共聚焦显微镜对磨痕轮廓及磨痕表面进行分析,探讨在300和500℃温度下TC4合金在不同位移幅值作用下的微动磨损机制。实验结果表明：高温条件下,试样平均摩擦因数和磨损率随位移幅值的增加呈现先增大后减小的趋势;两种高温环境中,小位移幅值时,微动运行区域为部分滑移区,主要损伤机制为黏着磨损和氧化磨损;位移幅值为100μm时,微动运行区域为混合滑移区,主要磨损机制为氧化磨损、剥层磨损及塑性变形;大位移幅值时,微动运行区域为完全滑移区,主要磨损机制为磨粒磨损和疲劳磨损。对比300和500℃条件下磨损结果,表明温度越高TC4合金耐磨性能越好,这主要是由于摩擦生成的氧化物TiO₂和Fe₂O₃对磨损表面具有保护作用。     

刃口钝化对高速钢丝锥耐磨性及寿命的影响

以W6Mo5Cr4V2高速钢丝锥为研究对象,首先运用电解强化技术对丝锥进行钝化处理,得出不同钝圆半径丝锥;然后进行攻丝试验,通过对丝锥切削齿后刀面磨损值VB的测量和寿命的检测确定丝锥最优钝圆半径;再分别对未钝化与最优钝圆半径丝锥进行典型磨损曲线的绘制。最后对这两组丝锥进行攻丝扭矩的测量,得出丝锥在加工过程中扭矩的变化规律。结果表明:钝圆半径为15μm的丝锥寿命提高最明显,约为未钝化丝锥的2.5倍;两组丝锥的磨损过程都符合典型磨损曲线的发展趋势,经钝化处理后的丝锥磨损值小、磨损速率慢;在初期磨损阶段,未经钝化处理的丝锥扭矩比钝化处理后丝锥的小,但波动范围较大,加工过程不稳定;整个切削过程未钝化丝锥扭矩增长速率快,丝锥很快失效。     

农机刀片的磨损机理和碳化物在磨损中的行为

通过扫描电镜对大量农机刀片进行失效分析，分别研究了刃口和刃面的磨损机理，认为在刃面上有适应当数量和形态的与基体结合牢固的碳化物能提高刃面抗划伤能力，而刃口上的碳化物则会促使崩刃。据此，提出两种改变碳化物分布形态的热处理新工艺，取得很好的效果。     

高温场对滚动轴承游隙的影响

建立了滚动轴承在高温热场中的保温筒有限元模型,运用ANSYS分析了其在高温场中的温度分布,并结合摩擦学和传热学理论分析其在高温场中的径向变形规律,计算其径向游隙减小量。结果表明:在高温场中,滚动轴承的径向游隙随环境温度的升高而减小,对游隙影响较大的是内圈沟道的变形,且300℃以后游隙减小量的变化趋向平缓。