Effects of reinforcement on wear resistance of aluminum matrix composites

The effect of reinforcement on the wear mechanism of metal matrix composites （MMCs） was investigated by considering different parameters, such as sliding distance （6 km）, pressure （0.14-1.1 MPa） and sliding speed （230-1480 r/min）. The wear mechanisms of an MMC and the corresponding matrix material under similar experimental conditions were compared on a pin-on-disc wear machine. The pins were made of 6061 aluminum matrix alloy and 6061 aluminum matrix composite reinforced with 10% Al2O3 （volume fraciton） particles （6-18μm）. The disc was made of steel. The major findings are as follows： the MMC shows much higher wear resistance than the corresponding matrix material; unlike that of matrix material, the wear of MMC is very much linear and possible to predict easily; the wear mechanism is similar for both materials other than the three-body abrasion in the case of MMC; the reinforced particles resist the abrasion and restrict the deformation of MMCs which causes high resistance to wear. These results reveal the roles of the reinforcement particles on the wear resistance of MMCs and provide a useful guide for a better control of their wear.

Microstructure,mechanical properties and wear resistance of Ti particles reinforced AZ31 magnesium matrix composites

The compromise between strength and plasticity has greatly limited the potential application of particles reinforced magnesium matrix composites(MMCs).In this work,the Ti particles reinforced AZ31 magnesium(Mg)matrix composites achieved simultaneous improvement in strength,elongation and wear resistance.The Ti particles reinforced AZ31 composites were fabricated by ultrasonic-assisted stir casting with hot extrusion.The results showed that a strong interfacial bonding was obtained at Ti/Mg interface because of the formation of semicoherent orientation relationship of Ti Al/Mg,Ti Al/Al_(2)Ti and Al_(2)Ti/Mg interfaces.The as-extruded 6 wt.%Ti/AZ31 composite presented the best compressive mechanical properties and wear resistance with ultimate tensile strength,elongation and wear rate of 327 MPa,20.4%and 9.026×10^(-3)mm^(3)/m,obviously higher than those of AZ31 alloys.The enhanced mechanical properties were attributed to the grain refinement and strong interfacial bonding.The improved wear resistance was closely related to the increased hardness of composites and the formation of protective oxidation films.

Microstructure,mechanical properties,and wear resistance of VCp-reinforced Fe-matrix composites treated by Q&P process

A quenching and partitioning(Q&P) process was applied to vanadium carbide particle(VCp)-reinforced Fe-matrix composites(VC-Fe-MCs) to obtain a multiphase microstructure comprising VC, V8 C7, M3 C, α-Fe, and γ-Fe. The effects of the austenitizing temperature and the quenching temperature on the microstructure, mechanical properties, and wear resistance of the VC-Fe-MCs were studied. The results show that the size of the carbide became coarse and that the shape of some particles began to transform from diffused graininess into a chrysanthemum-shaped structure with increasing austenitizing temperature. The microhardness decreased with increasing austenitizing temperature but substantially increased after wear testing compared with the microhardness before wear testing; the microhardness values improved by 20.0% ± 2.5%. Retained austenite enhanced the impact toughness and promoted the transformation-induced plasticity(TRIP) effect to improve wear resistance under certain load conditions.

Recent advances in self-lubricating metal matrix nanocomposites reinforced by carbonous materials:A review

Metal matrix self-lubricating materials lie at the core of cutting-edge aerospace,mechanical,and electrical industries,which demand technological performances that cannot be met by traditional liquid lubricants.Rapid innovation in nanocarbon materials in recent years enabled rapid development of advanced nanocomposites for applications in structural engineering and functional devices.Carbonous materials(e.g.,graphite,graphene and carbon nanotubes),exhibit a wide range of unique electrical,mechanical,and thermal properties,which are also considered ideal lubricating reinforcements for metal matrix nanocomposites(MMCs)with superior mechanical and tribological properties.In this review,we first showcase the distinctive features of the constituents commonly employed in self-lubricating MMCs,encompassing the high-strength metallic matrix and nano-carbonous reinforcement.Then,we present a comprehensive overview of the recent advancements in preparation techniques for these advanced MMCs,followed by an in-depth discussion on their corresponding tribological properties and wear mechanisms.We close this review by outlining key problems to be solved and the future trend of the development in self-lubricating MMCs.

Wear resistance of surface metal matrix composite produced by gas tungsten arc melt injection of Cr3C2 -NiCr particles into low carbon steel

Cr3 C2-NiCr particles were injected into the melted surface of Q235 low carbon steel to make a surface metal matrix composite （MMC） layer by gas tungsten are melt injection （GTAMI） process. Hardness of the surface MMC layer was tested. Wear resistance of the surface MMC was investigated with a ball-on-disk dry sliding setup. Microstrnetures of the surface MMC layer and morphology of the worn surfaces were investigated with scanning electron microscopy （SEM）. The results showed that the hardness of the MMC was as high as 1 960. 7 HV. Wear loss of the upper part of the MMC layer is onlyO. 8% of that of the substrate under the dry sliding condition given. Wear loss of the bottom part is 2. 5 % of that of the substrate.

HARDNESS PROPERTY AND WEAR RESISTANCE OF Al_2O_(3P)/ Zn-Al COMPOSITE

The hardness values and the wear resistance of Al2O3P/ Zn-Al composite, prepared by means of rheological casting technology,are investigated separately in this work. The results show that the addition of Al2O3P increases the hardness values of the matrix at both room and high temperature and improves the wear resistance of the material.The hardness values and the wear resistance of the composite rise with the increase of the particle volume fraction or the decrease of the particle size.The raising of test temperature results in a rapid descending of its hardness values.However, the addition of Al2O3P improves the property of high temperature resistance of Zn-Al alloys significantly.Moreover,the effect of quenching, tempering or cycling heat treatment on the hardness values of the composite is also studied.

Effect of graphite content on wear property of graphite/Al_2O_3/Mg-9Al-1Zn-0.8Ce composites

Using squeeze-infiltration technique, Mg-9Al-1Zn-0.8Ce composite reinforced by graphite particles and Al2O3 short fibers was fabricated. The reinforcing phases combined closely with the matrix and no agglomeration was observed. The microstructure, hardness and wear property of the composites with the graphite content of 5%, 10%, 15% and 20% were investigated, respectively. The results reveal that Ce tends to enrich around the boundaries of graphite particles and Al2O3 short fibers, and forms Al3Ce phase. When the graphite content increases to 20%, the grain size becomes small. Moreover, with increasing the graphite content, the microhardness of the composites decreases but the wear resistance increases. The graphite which works as lubricant during dry sliding process decreases the wear loss. At low load, the wear mechanism of the composite is mainly abrasive wear and oxidation wear; at high load, except that the composite with 20% graphite is still with abrasive wear and oxidation wear, the wear mechanism of other composites changes to delamination wear.

Improving wear and corrosion resistances of Mg_(2)Si/AZ91 composites via tailoring microstructure and intrinsic properties of Mg_(2)Si induced by Sb modification

To achieve simultaneous improvement in wear resistance and corrosion resistance,we propose a novel strategy to successfully develop Mg matrix composites containing blocky primary Mg_(2)Si with small size instead of undesirable dendrite shape and large size.The tribological and corrosion behavior of Mg_(2)Si/AZ91 unmodified and modified with 2.0wt.%Sb was subsequently and systematically investigated.The results show that Sb addition can significantly modify the morphology of primary Mg_(2)Si to blocky polygon with smaller size of 12-25μm,but has less effect onα-Mg grain size.Compared with unmodified composite,Sb modified Mg_(2)Si/AZ91 composite has higher Brinell hardness and nearly unchanged microhardness of the matrix.Sb modified composite exhibits a 26%lower wear loss than unmodified composite suggesting the greatly improved wear resistance.Microstructure analyses indicate that the main wear mechanism of composites is dominated by abrasive wear,and Sb addition can decrease the width and depth of grooves,resulting in a weakened abrasive wear behavior.Additionally microcracks initiation on Sb modified Mg_(2)Si particles can be restricted during the sliding friction process because of higher toughness and blocky polygonal shape induced by Sb doping,which is responsible for the improved wear resistance.Interestingly,Sb modified Mg_(2)Si/AZ91composite also demonstrates a superior corrosion resistance than unmodified composite due to the decrease of calculated corrosion rate from1.57 mm/y to 0.74 mm/y,reduced by 52.8%.Such improvement is closely related to the reduced susceptibility to micro-galvanic corrosion,which is attributed to the reduced volta potential difference of Mg_(2)Si relative to the Mg matrix,from 365 mV to 210 mV.

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.

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.

Wear Properties of Plasma Transferred Arc Fe-based Coatings Reinforced by Spherical WC Particles

Fe-based coatings reinforced by spherical WC particles were produced on the 304 stainless steel by plasma transferred arc(PTA) to enhance the surface wear properties. Three different Fe/WC composite powder mixtures containing 0 wt%, 30 wt%, and 60 wt% of WC were investigated. The microstructure and phase composition of the Fe/WC composite PTA coatings were evaluated systemically by using scanning electron microscope(SEM) and X-ray diffraction(XRD). The wear properties of the three fabricated PTA coatings were investigated on a BRUKER UMT TriboLab. The morphologies of the worn tracks and wear debris were characterized by using SEM and 3 D non-contract profiler. The experimental results reveal that the microhardness on the cross-section and the wear resistance of the fabricated coatings increase dramatically with the increasing adding WC contents. The coating containing 60 wt% of WC possesses excellent wear resistance validated by the lower coefficients of friction(COF), narrower and shallower wear tracks and smaller wear rate. In the pure Fe-based coating, the main wear mechanism is the combination of adhesion and oxidative wear. Adhesive and two-body abrasive wear are predominated in the coating containing 30 wt% of WC, whereas threebody abrasion wear mechanism is predominated in the coating containing 60 wt% of WC.

Effect of glucose concentrations on wear resistance of Al/APC composites prepared by hydrothermal carbonized deposition on chips

In this study,a novel method termed hydrothermal carbonized deposition on chips(HTCDC)is proposed to prepare aluminum alloy-amorphous carbon(Al/APC)composites.The influences of glucose concentration in hydrothermally reaction on the microstructure and wear resistance of the Al/APC composites were thoroughly studied.Amorphous carbon was deposited by HTCDC onto Al–20Si chips as a supporter.The Al/APC composites were prepared by hot extrusion from the chips.The results indicated that a uniform carbon film was successfully synthesized on the surface of the chips,improving the wear resistance of the Al/APC composites.With increasing concentration of glucose solution,the size and the number of delamination on the wear surface and the coefficient of friction decreased,and the wear rate decreased at first and then increased.In addition,the dehydration and carbonization processes in the hydrothermal reaction of glucose were analyzed.A schematic model of the wear surface of the Al/APC composites was established and the wear mechanisms were discussed.

STUDY ON THE SiC_p./Al-ALLOY COMPOSITE AUTOMOTIVE BRAKE ROTORS

The SiCp/Al-alloy composite front brake rotors designed for Shanghai Santana cars were prepared by semi-solid stirring+liquid forging process. The composite brake rotors were subjected to dynamometer tests on a SCHENCK brake testing system, referring to TL110 standard of VOLKSWAGEN Co. The friction coefficient and thermal response during fade testing and the wear performance of the composite rotors were studied as the functions of various parameters such as braking pressures, initial speeds, initial temperatures, torque and decelerations, and were compared with those of conventional cast iron rotors. The results show that the properties of the composite rotors can achieve the requirements of commercial cast iron rotors. The results also show that the friction coefficients of the composite rotors under different braking conditions are within the deviation band specified by the TL110 standard, and the temperature rise of composite rotors is lower than that of cast iron rotors at the end of each fade stop. The wear resistance of composite rotors is higher than that of cast iron rotors. The friction mechanism and wear mechanism were analyzed.

Fe-Cr基陶瓷复合耐磨材料绝热温度的热力学计算

根据热量平衡的关系,对不同Fe/Cr质量比和硬质相含量下,Fe-Cr基陶瓷复合耐磨材料Al-Fe3O4-CrO3-B4C-Ti系的绝热温度进行计算。结果表明:m(Fe)∶m(Cr)=4∶1~9∶1时,硬质相的质量分数由10%增加到40%,Al-Fe3O4-CrO3-B4C-Ti系的绝热温度均大于1800 K,燃烧合成反应能自持;m(Fe)∶m(Cr)=7∶1~9∶1时,随两者质量比的降低,反应体系绝热温度的增加幅度不大;m(Fe)∶m(Cr)<6∶1时,反应体系的绝热温度增加幅度较大。通过燃烧合成实验验证了体系绝热温度理论计算结果的正确性,基于热力学计算分析及燃烧合成实验结果综合考虑,最佳的m(Fe)∶m(Cr)=6∶1,硬质相的质量分数为30%。

混杂颗粒增强Ni基复合材料的冲蚀磨损性能研究

煤炭开采、石油化工等极端工况条件下的机械装备对部分关键零部件材料的磨损性能提出了更高要求。本研究设计制备了大尺寸氧化锆颗粒(ZTAp)承载与小尺寸碳化钨颗粒(WCp)强化基体相结合的混杂颗粒增强金属基复合材料,研究了介质、冲蚀角度、ZTAp尺寸、WCp含量对复合材料冲蚀磨损性能的影响及其机理。结果表明,适量ZTAp、WCp的添加能够显著提高复合材料的抗冲蚀磨损性能。固定体积分数的ZTA颗粒,尺寸越大,复合材料冲蚀磨损性能越好,其主要失效形式为脆性剥落和疲劳断裂。WC颗粒通过第二相增强、固溶强化以及析出强化的方式,提高了基体的硬度和耐磨性,抑制了酸性介质中腐蚀与磨损的交互作用,冲蚀过程中主要失效形式为脆性断裂剥落。

热处理对GNP-Al复合材料显微组织和性能的影响

本文以石墨烯为增强相,采用高能超声辅助铸造法及后续热处理制备了铝基复合材料,并研究石墨烯和热处理对复合材料显微组织、力学性能和耐磨性能的影响。结果表明,石墨烯促进了复合材料晶粒细化,且热处理后Si相进一步细化及圆整。经热处理后复合材料的屈服强度和抗拉强度(245和319MPa)比基体(119和202MPa)分别提高了105.9%、57.9%。磨损试验结果表明,添加石墨烯和T6热处理后复合材料的磨损率最低,磨损机制由剥层磨损转变为磨粒磨损。

激光熔覆WC/316L复合涂层结构及磨损性能

为改善激光熔覆过程中WC增强金属基复合涂层分解与分布不均匀的问题,采用激光熔覆技术制备了50%WC含量的WC/316L复合涂层,分别采用扫描电子显微镜(SEM)、显微维氏硬度计、摩擦磨损试验机表征了熔敷层的组织形貌、硬度与摩擦磨损性能。结果显示,低热输入量可以防止WC颗粒下沉,提升熔覆层厚度方向上的WC颗粒分布均匀性;但WC的平面分布均匀性较差,同时低热输入导致WC颗粒结合较弱,易发生脱落;熔覆过程中,粉末中15%的WC发生分解。研究表明,通过降低激光热输入量,可以制备WC厚度方向较为均匀的复合涂层,提升熔覆层耐磨性,但是需要优化WC平面分布均匀性与WC颗粒结合性能。

壳核结构氧化铝@石墨烯复合粉末增强铜基复合材料摩擦学性能研究

如何充分发挥润滑组元和耐磨组元的协同作用以提高铜基复合材料摩擦学性能仍面临具大的挑战。以石墨烯为润滑组元,氧化铝为耐磨组元,对比了氧化铝和石墨烯组装为壳核结构前后对铜基复合材料摩擦学性能的影响。结果表明,与氧化铝和石墨烯分别以独立相分布于铜基体的情况相比,氧化铝和石墨烯组装为壳核结构后可以提高铜基复合材料的致密度、硬度,并有利于在磨痕表面形成连续且具有保护性的摩擦层。因此,在10~40 N载荷范围内干摩擦,后者比前者具有更低的摩擦因数和磨损率。

双尺度SiC_(p)增强Al基复合材料的制备及耐磨性研究

采用粉末冶金法制备了双尺度SiC_(p)增强Al基复合材料,SiC_(p)双粒径50μm:10μm的比例分别为1∶1、2∶1、3∶1、4∶1及5∶1,添加总含量为20vol%。通过销盘式摩擦磨损试验机对复合材料及对比试样HT300材料的耐磨性能进行了测试,使用SEM、EDS对复合材料及HT300摩擦磨损前后的微观形貌进行了表征,并对复合材料摩擦磨损机理进行了分析。结果表明,SiC_(p)与Al基体界面结合良好,无界面脱粘及孔隙产生。任一碳化硅颗粒粒径配比的SiC_(p)/Al基复合材料的耐磨性能均优于HT300,其中颗粒粒径配比为3∶1时耐磨性能最优,HT300磨损量约为颗粒粒径配比3∶1时的7~13倍。

石墨烯化学镀铜对放电等离子烧结石墨烯增强铝基复合材料组织和性能的影响

通过化学镀方法得到镀铜石墨烯粉末,再通过静电自组装方法将镀铜石墨烯粉末与铝粉混合,然后经放电等离子烧结工艺制备镀铜石墨烯增强铝基复合材料,研究了不同质量分数(0.1%,0.2%,0.3%,0.4%,0.5%)镀铜石墨烯增强铝基复合材料的微观结构和性能,并与质量分数0.1%未镀铜石墨烯增强铝基复合材料进行对比。结果表明:镀铜石墨烯在复合材料中分散均匀,复合材料的相对密度均在99%以上;铝和铜发生反应生成了中间相Al_(2)Cu,但未有Al_(4)C_(3)界面相生成;镀铜石墨烯增强铝基复合材料的硬度和耐磨性能均优于未镀铜石墨烯增强铝基复合材料;随着镀铜石墨烯含量的增加,复合材料的硬度先升高后降低,磨损质量损失和摩擦因数均呈先减小后增加的趋势。当镀铜石墨烯的质量分数为0.2%时,复合材料具有优异的综合性能,其硬度为74.7 HV,磨损质量损失和摩擦因数均最小,分别为0.0023 g和0.259,磨损机制为氧化磨损。