7075铝合金板材热冲压成形中的高温摩擦

采用自制的板带高温摩擦试验机模拟实际固溶–冲压–淬火一体化热成形工艺下7075铝合金的高温摩擦过程,分别对上下摩擦头进行冷却和加热以模拟实际热冲压过程对模具和压边圈的冷却和加热,分析了下模加热温度、法向载荷和滑动速度对7075铝合金摩擦行为及磨损机理的影响。结果表明:铝合金摩擦系数随着下模加热温度的升高而增大,磨损机制由300 ℃时的黏着磨损转变为500 ℃时的黏着磨损、氧化磨损和磨粒磨损;施加法向载荷越大,摩擦系数越大,不同载荷下磨损机制均为黏着磨损及轻微的磨粒磨损,且随着载荷增大,黏着磨损程度有所加深;高滑动速度导致了磨损表面局部氧化物的生成,使摩擦系数随着滑动速度增大而减小,滑动速度为30 mm·s?1时,磨损机制主要是氧化磨损、磨粒磨损和黏着磨损。      

Effect of rare earths surface treatment on tribological properties of carbon fibers reinforced PTFE composite under oil-lubricated condition

The effect of rare earths （RE） surface treatment of carbon fibers （CF） on tribological properties of CF reinforced polytetrafluoroethylene （PTFE） composites under oil-lubricated condition was investigated. Experimental results revealed that RE treated CF reinforced PTFE （CF/PTFE） composite had the lowest friction coefficient and wear under various applied loads and sliding speeds compared with untreated and air-oxidated composites. X-ray photoelectron spectroscopy （XPS） study of carbon fiber surface showed that, after RE treatment, oxygen concentration increased obviously, and the amount of oxygen-containing groups on CF surfaces were largely increased. The increase in the amount of oxygen-containing groups enhanced interfacial adhesion between CF and PTFE matrix. With strong interfacial adhesion of the composite, stress could be effectively transmitted to carbon fibers; carbon fibers were strongly bonded with VITE matrix, and large scale rubbing-off of PTFE be prevented, therefore, tribological properties of the composite was improved.     

NM400/NM500级矿山机械用钢的高温磨损性能及机理

将直径为5 mm的混合烧结Al₂O₃陶瓷球安装在高温滑动摩擦试验机夹持工具上与耐磨钢组成摩擦副, 研究了耐磨钢与氧化铝陶瓷球在200~300 N、100~400 r·min-1不同载荷下的滑动摩擦行为.结合X射线衍射分析技术和扫描电镜等分析手段研究了NM400和NM500两种耐磨钢在室温~300℃下摩擦界面处材料的氧化物形成、磨损表面形貌和显微组织等行为.随温度升高, NM400和NM500的摩擦系数仍然处于0.27~0.40的范围内, 但两者的平均摩擦系数分别从0.337、0.323逐步降低至了0.296和0.288.在300℃时, 氧化物的产生是摩擦系数略有下降的主要原因.随着温度的升高, 摩擦行为首先以磨粒磨损为主, 随后逐渐发生氧化物的压入-剥离-氧化现象, 使磨损速率略有降低.通过高温摩擦磨损行为与微量氧化模型的分析发现, NM400和NM500钢在室温至300℃的磨损机制是磨粒磨损、挤压变形磨损以及微量氧化物磨损的共同作用.NM500钢表现出更加良好的耐磨性能主要原因是其硬度强度高于NM400钢.在高强微合金马氏体耐磨钢中添加少量合金元素, 使其在高温摩擦过程中产生一定量稳定附着的氧化物, 在一定程度上能够起到降低磨损率的作用.      

列车制动用Cu基粉末闸片材料摩擦磨损性能分析

列车的制动性能与闸片材料的摩擦磨损性能关系密切,在MM-1000Ⅱ型摩擦试验机上测试了自制的Cu基粉末列车闸片材料在不同制动速度下的摩擦磨损特性。结果表明:随着制动速度的增大,摩擦表面的微凸起遭到破坏,摩擦因数随之降低,磨损量增加;在材料接触表面产生大量的摩擦热,造成基体软化,减小了基体对材料中SiO_2等硬质颗粒的夹持能力。摩擦因数和稳定系数均随制动速度增加而降低;而摩擦温度和磨损量随制动速度增加而提高,尤其是在制动速度大于8 r/s时,摩擦表面温度上升,造成基体软化,硬质颗粒脱落,加速了材料的摩擦磨损。为列车制动用Cu基粉末闸片材料摩擦磨损性能的研究提供了理论基础。     

微晶玻璃与硬质合金摩擦磨损实验研究

根据微晶玻璃陶瓷与硬质合金对磨实验,研究摩擦系数和磨损率的变化规律,对陶瓷盘和金属销磨损表面形貌进行观察,并进行分析。实验数据显示,微晶玻璃与硬质合金的平均摩擦系数为0.10,在低载荷条件下,微晶玻璃的磨损率较大,随着载荷增大,微晶玻璃的磨损率下降。     

氟金云母玻璃陶瓷摩擦磨损性能研究

在MPX-2000型摩擦磨损试验机上考察了不同载荷下氟金云母玻璃陶瓷与碳钢对摩时的摩擦磨损性能,用金相显微镜观察和分析磨损表面形貌,测试了摩擦系数和玻璃陶瓷的磨损率,并探讨了材料的磨损机理。结果表明,随着载荷的增加,摩擦副的摩擦系数明显增大,有较大波动。     

高氮不锈轴承钢的微动磨损性能

为了探究应力和滑动速度对高氮不锈轴承钢微动磨损性能的影响,采用SRV-Ⅳ微动磨损试验机进行了不同应力和不同滑动速度下的微动磨损试验,对摩擦因数和磨损率进行分析,并对磨斑形貌进行观察.结果表明:试验钢的摩擦因数随应力和滑动速度的增加而减小;磨损率随应力和滑动速度的增加而增加.随着pv值(表示轴承工况的严重程度)的增大,高氮不锈轴承钢的磨损机理由黏着磨损逐渐转变为磨粒磨损和塑性挤出磨损.     

Load and sliding velocity effect in dry sliding wear behavior of CuZnAl shape memory alloys

The wear behavior of shape memory alloys is linked to the thermoelastic martensitic transformation. Due to this transformation, these alloys have the ability to absorb a high amount of energy before undergoing plastic deformation and subsequent fractures caused by wear. In this study, the effect of sliding velocity and load on the dry wear behavior of CuZnAl alloys has been characterized. Weight loss as a function of the M_s transformation temperature at different sliding velocities and loads was studied for the different alloys. The weight loss and friction coefficient of the alloys as a function of load showed linear and exponential relationships, respectively; however, when considered versus applied sliding velocity, independently of which phase was present, they showed an exponential relation and no direct relation, respectively.     

Dry sliding friction and wear in plain carbon dual phase steel

In view of the potential of plain carbon dual phase (DP) steel as wear resistant material, the wear and friction characteristics of this steel, which consists of hard martensite islands embedded in a ductile ferrite matrix, have been investigated and compared with those observed in plain carbon normalized (N) steel that has the same composition of 0.14 wt pct carbon. Dry sliding wear tests have been carried out using a pin-on-disk wear testing machine at normal loads of 14.7, 24.5, and 34.3 N and at a constant sliding velocity of 1.15 m/s. Weight loss in the samples has been measured over time on the same specimen, and the variation of cumulative wear loss with sliding distance has been described by two linear segments, for both the DP and the N steel. At these loads, the mechanism of wear is primarily oxidative, although subsurface cracking and delamination wear could also be observed in a few places. The second linear segment could result from a dynamic steady state wear of the transfer layer of compacted oxide wear debris on the sliding surfaces. The wear rate calculated on the basis of the first linear segment varies linearly with normal load, which is indicative of Archard’s law, and it is significantly lower for the DP steel than for the N steel. The wear rate calculated on the basis of the second linear segment, however, varies with load linearly for the DP steel but nonlinearly in the N steel. In the first linear segment, the wear coefficient is about 0.39 × 10⁻⁴ for the DP steel and is 0.40 × 10⁻⁴ for the N steel. Higher hardness and, consequently, a lower real area of contact in the DP steel at all the loads have compensated for the lower wear rates, and have resulted in a wear coefficient similar to that in the N steel. The steady state wear coefficient from the second linear segment is 0.29 × 10⁻⁴ for the DP steel at all loads; for the N steel, these are 0.21 × 10⁻⁴ and 0.64 × 10⁻⁴, respectively, for lower and higher loads.     

Al-Zn-Mg合金高温摩擦磨损行为研究

采用高温摩擦磨损试验机,在25～500℃的试验温度和1～5 N法向载荷下对Al-Zn-Mg合金进行球盘摩擦试验,分析不同试验温度和法向载荷下Al-Zn-Mg合金摩擦系数变化、磨损表面及亚表层的形貌特征和成分特征,研究了试验温度和法向载荷对Al-Zn-Mg合金摩擦行为的影响.结果表明:载荷为5 N时,在25～500℃温度...     

Effect of martensite content on friction and oxidative wear behavior of 0.42 Pct carbon dual-phase steel

In order to explore the tribological potential of the dual-phase (DP) steel as a wear-resistant material, the friction and wear characteristics have been investigated for this steel with varying amounts of martensite from 42 to 72 vol pct, developed by varying holding time at the intercritical annealing temperature of 740 °C. Dry sliding wear tests have been conducted on DP steels containing 0.42 wt pct carbon using a pin-on-disk machine under different normal loads of 14.7, 19.6, 24.5, 29.4, and 34.3 N and at a constant sliding speed of 1.15 m/s. Weight loss has been measured at different time intervals on the same specimen. The variation of cumulative volume loss with sliding distance has been represented by two linear segments signifying the run-in and the steady state of wear. The mechanism of wear is primarily oxidative in nature, which has been confirmed by X-ray diffraction patterns of the wear debris generated during sliding. The wear rate varies linearly with load in both the run-in and the steady state. The wear rate decreases linearly with increasing volume fraction of martensite in DP steels reflecting the effect of hardness imparted by the increasing amount of martensite, which is a hard and load bearing phase. The average coefficient of friction also decreases linearly with increasing load as well as with increasing martensite volume fraction. In the run-in stage, the wear coefficient does not change significantly between DP1 and DP2 steels containing 42 and 51 vol pct martensite, respectively, but decreases sharply as one moves from DP2 to DP4 containing, respectively, 51 and 72 vol pct martensite. But in the steady state, the wear coefficient decreases almost linearly with increasing volume fraction of the martensite. The decrease in wear coefficient may be attributed to the decreasing wear rate dominating over the decrease in real area of contact due to increasing hardness.     

Influence of loading and rotation speed on Friction and Wear properties of CuAlBi Alloy

The variation of the friction coefficient of the CuAlBi alloy at different connecting loading and friction speed were investigated by using MMU-5G sliding friction-wear tester, besides, the wear mass loss of the CuAlBi alloy was measured, and the influence of loading and rotation speed on friction and wear properties of CuAlBi alloy was also discussed. The results show that the friction coefficient increase then decrease with increase of connecting loading as well as decreases with increase of friction speed, and the wear loss mass increases with increase of connecting loading and friction speed. As a result, the wear failure form of CuAlBi alloy is mainly ploughing.     

表面纳米化对低碳钢在干摩擦条件下摩擦磨损性能的影响

采用表面机械研磨的方法对低碳钢板材进行表面处理.经X射线衍射及透射电镜分析表明处理后的试样形成了一定厚度的具有纳米晶粒结构的表层.用立式万能摩擦试验机研究处理后试样在干摩擦条件下的摩擦磨损性能,通过分析其磨损表面形貌,探讨表面纳米化对低碳钢磨损行为的影响.结果表明在载荷为15～75N条件下,其摩擦系数较未处理样品明显降...     

不锈钢耦合变形摩擦有限元分析

针对奥氏体不锈钢成形过程中的摩擦磨损问题,设计了一种耦合变形摩擦的试验方法,在实验中分析了耦合摩擦试验中钢带滑动速度对钢板与压头间的摩擦系数的影响。通过对磨损表面进行观察,以及LS DYNA仿真对应力的分析发现：滑动速度的增加引起了剪切应力的增加,钢带试样的马氏体组织转变量随着其滑动速度的增加而增加,并引起摩擦表层马氏体组织磨粒磨损,表面磨损现象加重,且摩擦系数波动减小。     

悬浮聚合酚醛树脂基制动材料的摩擦学性能

采用悬浮聚合法制备热固性酚醛树脂,通过红外光谱分析和热重分析对该悬浮聚合酚醛树脂(suspension-polymerization phenolic resin,缩写为SPPR)的结构和热学性能进行分析。用模压成形工艺制备树脂基制动复合材料,利用JF150D-II型摩擦磨损试验机测试该材料与HT250灰铸铁在100～350℃盘面温度范围内的滑动摩擦性能。结果表明,SPPR的热分解温度为396℃,在400℃时质量损失率为12.7%,具有较好的热稳定性。经过正交试验得到树脂基制动复合材料的优化配方,制备的复合材料和HT250灰铸铁对摩,在100～350℃升温过程中,摩擦因数平均值为0.41,波动值为0.07,350℃的摩擦因数和最大摩擦因数的比值(μ350℃/μmax)为1。和国内外优质产品相比,该复合材料的摩擦因数适中,磨损率较低,摩擦稳定性和抗热衰退性能优异。     

Effect of Oxide Content on the Tribological and Physicomechanical Properties of Filled Polytetrafluoroethylene

The effect of the nature and the amount of oxide fillers on antifriction properties of polytetrafluoroethylene under dry friction conditions with different loads and slow sliding rates is studied. It is established that oxides with a high hardness increase the friction coefficient and reduce the wear resistance of filled polytetrafluoroethylene, but oxides with a low hardness do not give rise to an increase in friction coefficient for polytetrafluoroethylene with a marked increase in its wear resistance, and this is connected with formation of a separating layer at the surface of the friction pair.     

不锈钢与地铁集电靴用浸金属碳材料的摩擦磨损性能研究

利用销-盘式高速摩擦磨损试验机研究了工况因素（电流、滑动速度和加载力）对地铁集电靴用浸金属碳材料与不锈钢盘试样载流摩擦磨损性能的影响，采用扫描电子显微镜与三维形貌仪对试样磨损表面进行观察与分析。结果表明，接触副摩擦系数随电流的增加而减小，随滑动速度和加载力的增加而增加；载流条件下，集电靴浸金属碳磨损量随电流、滑动速度和加载力的增加而增加；接触副磨损表面粗糙度随电流、滑动速度和加载力的变化情况与磨损量变化趋势相同。     

Cu/Mo_5Si_(3p)复合材料的摩擦磨损性能研究

采用销—盘式摩擦磨损试验机研究了液相烧结制备Mo5Si3颗粒弥散强化铜合金在滑动干摩擦条件下的摩擦磨损行为。结果表明:Cu/Mo5Si3p复合材料具有优良的摩擦磨损性能。随着Mo5Si3含量的增加Cu/Mo5Si3p复合材料的硬度增加,摩擦系数和磨损失重量降低。Mo5Si3含量低时,Cu/Mo5Si3p复合材料的磨损机制为犁沟变形和粘着磨损为主,而Mo5Si3含量高时则为犁沟变形磨损为主。     

Characterization and tribological behavior of cast In-Situ Al (Mg,Mo)-Al2O3 (MoO3) composite

Aluminum alloy—based cast in-situ composite has been synthesized by dispersion of externally added molybdenum trioxide particles (MoO₃) in molten aluminum at the processing temperature of 850 °C. During processing, the displacement reaction between molten aluminum and MoO₃ particles results in formation of alumina particles in situ and also releases molybdenum into molten aluminum. A part of this molybdenum forms solid solution with aluminum and the remaining part reacts with aluminum to form intermetallic phase Mo(Al_1−x Fe _x )₁₂ of different morphologies. Magnesium (Mg) is added to the melt in order to help wetting of alumina particles generated in situ, by oxidation of molten aluminum by molybdenum trioxide, and helps to retain these particles inside the melt. The mechanical properties of the cast in-situ composite, as indicated by ultimate tensile stress, yield stress, percentage elongation, and hardness, are relatively higher than those observed either in cast commercial aluminum or in cast Al-Mo alloy. The wear and friction of the resulting cast in-situ Al(Mg,Mo)-Al₂O₃(MoO₃) composites have been investigated using a pin-on-disc wear testing machine under dry sliding conditions at different normal loads of 9.8N, 14.7N, 19.6N, 24.5N, 29.4N, 34.3N, and 39.2 N and a constant sliding speed of 1.05 m/s. The results of the current investigation indicate that the cumulative volume loss and wear rate of cast in-situ composites are significantly lower than those observed either in cast commercial aluminum or in cast Al-Mo alloy, under similar load and sliding conditions. Beyond about 30 to 35 N loads, there appears to be a higher rate of increase in the wear rate in the cast in-situ composite as well as in cast commercial aluminum and cast Al-Mo alloy. For a given normal load, the coefficient of friction of cast in-situ composite is significantly lower than those observed either in cast commercial aluminum or in cast Al-Mo alloy. The coefficient of friction of cast in-situ composite increases gradually with increasing normal load while those observed in cast commercial aluminum or in cast Al-Mo alloy remain more or less the same. Beyond a critical normal load of about 30 to 35 N, the coefficient of friction decreases with increasing normal load in all the three materials.