Influence of rotational speed in friction surfacing of nickel-aluminide reinforced aluminum matrix composite on commercially pure aluminum

The effect of rotational speed in the friction surfacing of nickel-aluminide reinforced Al-Zn-Mg-Cu alloy matrix composite on commercially pure aluminum was investigated. The nickel-aluminide reinforcement was fabricated by in-situ methods based on adding nickel powders to Al-Zn-Mg-Cu alloy melt during the semi-solid casting process.The findings showed that an increase in the rotational speed from 600 to 1000 r/min raised the coating efficiency from 65% to 76%. Besides, there was no significant difference between coating efficiencies in the coating with and without nickel-aluminide. The outcomes showed that if the coating was applied at a rotational speed of 1000 r/min, a traverse speed of 100 mm/min, and an axial feeding rate of 125 mm/min, the hardness and shear strength of the substrate increased by up to 225% and 195%, respectively. But the wear rate of the substrate dropped by 75%. Although the hardness of the coating containing nickel-aluminide increases by up to 32% compared to the coating without nickel-aluminide, nickel-aluminide does not affect the thermal stability of the coating.

Tribological stability of particle reinforced aluminum matrix composites in braking

The tribological stability of particle reinforced aluminum matrix composites in braking was studied. Considering the requirements of the intention of present transportation field, high braking pressure and high initial braking rotating speed, as well as different reinforcement volume fractions were selected. The results indicate that under a systematic comparison with traditional braking material of cast iron, SiC particulate reinforced aluminum material composites (PRAMC) can retain stable friction coefficient in various braking pressures and rotating speeds. Even in a concrete course of braking, PRAMC can also maintain friction coefficient with little fluctuation. The existence of a uniform mass transfer layer adhering to the contact surface is an important prerequisite for maintaining a stable friction coefficient.

Microstructure and wear characterization of AA2124/4wt.%B4C nano-composite coating on Ti-6Al-4V alloy using friction surfacing

This work is focused on developing AA2124/4 wt.%B4 C nano-composite coatings on Ti-6 A1-4 V using friction surfacing to improve the wear resistance. The composite was produced using conventional stir casting method and coatings were laid using an indigenously-developed friction surfacing machine. The rotational speed of the mechtrode was varied. The microstructure of the composite coating was observed using conventional and advanced microscopic techniques. The sliding wear behavior was evaluated using a pin-on-disc apparatus. The coating geometry(thickness and width) increased with increased rotational speed. The interface was straight without thick intermetallic layer. Homogenous distribution of nano B4C particles and extremely fine grains was observed in the composite coating. The interfacial bonding between the aluminum matrix and B4C particles was excellent. The composite coating improved the wear resistance of the titanium alloy substrate due to the reduction in effective contact area,lower coefficient of friction and excellent interfacial bonding.

Effect of Al2O3sf addition on the friction and wear properties of (SiCp+Al2O3sf)/Al2024 composites fabricated by pressure infiltration

Aluminum(Al) 2024 matrix composites reinforced with alumina short fibers(Al_2O_(3sf)) and silicon carbide particles(SiC_p) as wear-resistant materials were prepared by pressure infiltration in this study. Further, the effect of Al_2O_(3sf) on the friction and wear properties of the as-synthesized composites was systematically investigated, and the relationship between volume fraction and wear mechanism was discussed. The results showed that the addition of Al_2O_(3sf), characterized by the ratio of Al_2O_(3sf) to SiC_p, significantly affected the properties of the composites and resulted in changes in wear mechanisms. When the volume ratio of Al_2O_(3sf) to SiC_p was increased from 0 to 1, the rate of wear mass loss(K_m) and coefficients of friction(COFs) of the composites decreased, and the wear mechanisms were abrasive wear and furrow wear. When the volume ratio was increased from 1 to 3, the COF decreased continuously; however, the K_m increased rapidly and the wear mechanism became adhesive wear.

Investigation on dry sliding wear behavior of Mg/BN nanocomposites

The present research objective is to investigate the effect of boron nitride nanoparticles reinforcement on dry sliding wear behavior of pure Magnesium and magnesium nanocomposites.The fabricated nanocomposites contains varied percentages of boron nitride such as 0%(pure Mg),0.5%,1.5%and 2.5%were synthesized by using powder metallurgy technique and followed by a hot working process called hot extrusion.The pin on disk equipment was used for conducting the wear tests for traditional loads of 5 N,7 N and 10 N at different sliding speeds of 0.6,0.9 and 1.2 m/s against the steel disk at room temperature.For all traditional loads and sliding speeds,the changes in wear rate and friction co-efficient(μ)with respect to sliding distances were observed and analyzed.The wear characteristics are observed with the help of scanning electron microscopy under given test conditions.To investigate dominant wear mechanisms for various test conditions,the morphologies of all worn composites surfaces were analyzed.Final results show that,for all nanocomposites the wear level raises with respect to the sliding speeds and loads.Magnesium reinforced with 0.5%boron nitride shows lower wear rates and low friction coefficient values compare with magnesium reinforced with 1.5%boron nitride and 2.5%boron nitride nanocomposites.

Microstructure and Tribological Behavior of Al2O3 Particle Reinforced Al Matrix Composites Fabricated by Spark Plasma Sintering

Nanoparticles and microparticles reinforced Al matrix composites were fabricated by spark plasma sintering, and the microstructure and tribological properties were investigated systemically. The nano-Al2O3 particle and micro-Al2O3 particle uniformly dispersed in Al matrix composites. The introduction of nanoparticles is beneficial to the decrease of friction coefficient and wear rate, while microparticles are responsible to the high friction coefficient, resulting in the abrasive wear. With the introduction of both nanoparticles and microparticles, their synergic effect will lead to the variation of tribological behavior.

Tribological behavior of self lubricating Cu/MoS_2 composites fabricated by powder metallurgy

The effects of MoS2 content on microstructure, density, hardness and wear resistance of pure copper were studied. Copper-based composites containing 0-10%（mass fraction） MoS2 particles were fabricated by mechanical milling and hot pressing from pure copper and MoS2 powders. Wear resistance was evaluated in dry sliding condition using a pin on disk configuration at a constant sliding speed of 0.2 m/s. Hardness measurements showed a critical MoS2 content of 2.5% at which a hardness peak was attained. Regardless of the applied normal load, the lowest coefficient of friction and wear loss were attained for Cu/2.5 MoS2 composite. While coefficient of friction decreased when the applied normal load was raised from 1 to 4 N at any reinforcement content, the wear volume increased with increasing normal load. SEM micrographs from the worn surfaces and debris revealed that the wear mechanism was changed from mainly adhesion in pure copper to a combination of abrasion and delamination in Cu/MoS2 composites.

Dry sliding wear behavior of Al_2O_3 fiber and SiC particle reinforced aluminium based MMCs fabricated by squeeze casting method

Al2O3 fiber （Al2O3f） and SiC particle （SiCp） hybrid metal matrix composites （MMCs） were fabricated by squeeze casting method.The tests were carried out using a pin-on-disk friction and wear tester by sliding these pin specimens at a constant speed of 0.36 m/s （570 r/min） against a steel counter disk at room temperature,100 C and 150 C,respectively.To observe the wear characteristics and investigate the wear mechanism,the morphologies of the worn surfaces and specific wear rate were analyzed by using scanning electron microscope （SEM） and Arrhenius plots.Moreover,the effects of fiber orientation and hybrid ratio were discussed.

Al-Mg-MnS复合材料的制备及性能

自润滑铝基复合材料有着密度小、比强度高、导电导热性好、热膨胀系数低、价格便宜等诸多优点。因此在航空航天、国防军工以及诸多民用领域都有着广阔的应用前景。在对Al-MnS复合材料的研究过程中,发现MnS与铝基体的界面存在润湿性较差的问题。因此,为了解决MnS颗粒与铝基体之间的界面结合问题,基于Mg元素在铝基体中具有较高的固溶度,在Al-MnS复合材料中加入Mg元素,采用粉末冶金方法制备Al-Mg-MnS复合材料。讨论了不同Mg元素含量对复合材料微观组织、力电性能、摩擦磨损性能的影响,并对润滑机理进行分析。结果表明:烧结过程中,Mg元素能显著改善复合材料的界面结合强度,进一步提高了复合材料的耐磨性能;当Mg元素含量为5%时复合材料的综合性能最优,抗拉强度为338 MPa,延伸率为10.9%;少量Mg元素的加入并不影响材料的导电率,可以获得综合性能优异的Al-Mg-MnS复合材料。

Cu层包覆CNTs与原位自生纳米相协同增强铝基复合材料的微观结构及力学性能

以纯铝粉末、CuO粉末和Cu层包覆CNTs为原料,采用快速热压烧结方法制备Al-CNTs(Cu)-CuO复合材料,研究不同质量分数的CuO对复合材料中原位反应生成相特征及其对材料力学性能和磨损性能的影响。研究结果表明:提高铝基复合材料中CuO含量会显著促进Cu层包覆CNTs增强铝基复合材料中Al_(2)Cu及Al_(2)O_(3)纳米相的原位析出,不仅提高了铝基复合材料的强韧性匹配度,而且降低了磨损率,提高了耐磨性能。Cu层包覆CNTs与原位自生纳米相协同强化作用可以有效地提升铝基复合材料的综合服役性能,其在航空航天、轨道交通等领域具有十分广阔的应用前景。

烧结温度对车用石墨-TiB_(2)增强铜基复合材料组织与性能的影响

采用真空热压烧结方法制备了石墨和TiB_(2)混杂增强Cu基复合材料,研究了烧结温度对复合材料微观结构、致密度、显微硬度、电导率和摩擦磨损性能的影响。结果表明:烧结过程中各粉末原料没有发生氧化,同时粉末之间也没有发生化学反应。两种增强相均匀地分散在连续的Cu基体中,同时颗粒之间没有形成聚集。随着烧结温度的升高,复合材料的致密度和显微硬度先增大后减小,摩擦系数和磨损率先减小后增大,电导率逐渐降低。烧结温度为800℃时,石墨和TiB_(2)混杂增强Cu基复合材料具有较优异的综合性能,其致密度、显微硬度、电导率、摩擦系数和磨损率分别为98.8%、92.2 HV0.1、43.2%IACS、0.213和1.757×10^(-5)mm^(3)/(N·m),磨损机制为显微切削为主,粘着磨损为辅。

铝基复合材料的摩擦磨损性能

在制动试验条件下，研究铝基复合材料的摩擦磨损性能研究结果表明；与铸铁材料相比，铝基复合材料能大大地降低摩擦表面温度，其摩擦系数可在较大载荷、较高转速下保持稳定，有利于制动性能的提高复合材料在不同摩擦试验后的磨损量与SiC含量和基体种类有关.在相同摩擦条件下,磨损量随颗粒含量增加而减少.与铸铁材料相比，它具有重量轻、导热快、摩擦系数稳定，不产生热裂，是较适宜的制动盘（毂）材料.

多壁纳米碳管/Cu基复合材料的摩擦磨损特性

利用销盘式磨损试验机研究了粉末冶金法制备的多壁纳米碳管 /Cu基复合材料的稳态摩擦磨损行为 ,并用扫描电镜分析了复合材料的磨损形貌。结果表明 :多壁纳米碳管 /Cu基复合材料具有较小的摩擦系数 ,并随纳米碳管质量分数的增加而逐渐降低 ;由于复合材料中纳米碳管的增强和减摩作用 ,在低载荷和中等载荷作用下 ,随着纳米碳管质量分数的增加 ,复合材料的磨损率减小 ;而在高载荷作用下 ,由于发生表面开裂和片状层剥落 ,含纳米碳管质量分数高的复合材料的磨损率增高。

高含量SiC颗粒增强铝基复合材料的增摩特性研究

汽车轻量化是当今汽车工业发展的主旋律.针对制动盘的轻量化,研究了SiC颗粒增强铝基复合材料与摩擦材料干滑动的摩擦行为,并探讨了其增摩的机理.结果表明:随SiC质量百分数从50%增加到55%,最大静摩擦系数增大了约80%.两对摩擦副的静摩擦系数随压力增大均明显增大,随滑动速度提高则呈先增后减的趋势.干滑动摩擦导致的摩擦表面温度升高造成基体软化,增强相脱落,且使得磨损机理由磨粒磨损向黏着磨损转变,从而严重影响摩擦系数的稳定性.

电磁铸造法制备的(Al_2O_3+Al_3Zr)_p/A359复合材料的磨损行为

利用A359-Zr(CO3)2体系原位反应合成法制备(Al2O3+Al3Zr)p/A359颗粒增强铝基复合材料,在制备过程中施加低频交变电磁场进行搅拌以提高复合材料的耐磨性能。干滑动摩擦磨损试验表明:复合材料的耐摩擦性比纯基体合金明显提高,施加电磁搅拌后复合材料的耐摩擦性进一步提高,特别是在较大载荷下的耐摩擦性大幅提高,从轻微磨损到急剧磨损的临界转变载荷由58.8N提高到78.8N。磨损表面的SEM分析显示:纯基体合金为粘着磨损和剥层磨损,复合材料的磨损为以磨粒磨损为主和少量的剥层磨损,施加电磁搅拌后的复合材料为纯磨粒磨损。

铝基石墨复合材料的摩擦特性与机理分析

研究了低速、低载荷滑动摩擦条件下铝基石墨复合材料的摩擦学特性．结果表明：在相对滑动初期，复合材料的摩擦系数与基体合金相近；随着摩擦过程的进行，复合材料的摩擦系数逐渐下降并最终趋于稳定；石墨含量越高，达到稳定摩擦系数所需的时间越短；摩擦系数的变化与摩擦表面石墨成膜过程相对应；摩擦系数达到稳定状态时自润滑膜覆盖面积大约为摩擦表面的８５％ ，这时自润滑膜在摩擦表面上生成和剥落过程达到动态平衡．

混杂铝基复合材料的摩擦系数模型

建立了碳化硅、石墨颗粒混杂增强铝基复合材料的摩擦系数模型。将混杂复合材料摩擦系数处理成无碳化硅时的石墨 -铝基复合材料摩擦系数分量、碳化硅对钢的刮擦从而引起的摩擦系数分量两部分之和。对两部分分量分别进行了建模和计算 ,然后相加得到混杂复合材料的总摩擦系数模型。通过与实验数据的比较 ,表明该模型能够较准确地计算较高石墨含量的混杂铝基复合材料的摩擦系数。

粉煤灰/铝-镁合金复合材料的微观组织及摩擦磨损性能

采用粉末冶金法制得粉煤灰/Al-25%Mg复合材料,研究不同粉煤灰含量对复合材料微观组织、硬度和摩擦磨损性能的影响,采用扫描电子显微镜观察复合材料的磨损表面形貌,并对其磨损机制进行探讨。结果表明:随着粉煤灰含量的增加,复合材料的硬度呈现先增大而后减小的趋势;在较低粉煤灰含量和较低载荷下,该复合材料的摩擦因数均低于基体铝合金的,并且随粉煤灰含量的增加复合材料的耐磨性有所提高,复合材料的磨损机制主要为粘着磨损和磨粒磨损;在较高粉煤灰含量和较高载荷下,该复合材料的磨损机制转化为以剥层磨损和磨粒磨损为主。

纳、微米Al_2O_3颗粒混杂增强铝基复合材料的磨损性能

利用搅拌摩擦加工（FSP）制备纳、微米氧化铝颗粒单一增强以及混杂增强的A356铝基复合材料，并在摩擦磨损试验机上考察其磨损性能。结果表明，在0．5～3．0MPa载荷范围内，在相同载荷下，混杂复合材料的磨损量都低于两种单一增强的复合材料；在不同载荷下，随着载荷的增加，复合材料的磨损量都增加，但是混杂颗粒增强复合材料的增加最快，微米颗粒增强复合材料最慢；复合材料的磨损机制主要是磨粒磨损和剥层磨损；在复合材料磨损亚表层都发现机械混合层的存在，对复合材料的耐磨性有一定的影响。

碳纤维毡增强铝基复合材料的摩擦磨损性能研究

采用压挤渗透工艺制备了新型碳纤维毡增强铝基复合材料 ,在 MG- 2 0 0 0型高速高温摩擦磨损试验机上考察了其摩擦磨损特性 .结果表明 :碳纤维毡增强铝基复合材料的摩擦磨损特性明显优于基体合金 ;复合材料经历由稳定磨损向严重磨损的转化 ;在稳定磨损阶段 ,复合材料的磨损表面存在由金属氧化物和碳膜共同构成的复合固体润滑膜 。