High-Temperature Tribological Behavior of Al-20Si-5Fe-2Ni/ZrB2 Composites

Abstract

In this work, Al-20Si-5Fe-2Ni/ZrB₂ composites with 0–20?wt% ZrB₂ were fabricated by spark plasma sintering. The effects of ZrB₂ content on the microstructure, mechanical properties and high-temperature tribological behavior of the composites were investigated. The results indicate that Si, Al₅FeSi, and ZrB₂ particles are uniformly distributed in the aluminum matrix. The density, hardness, and compressive strength increase with increasing ZrB₂ content. The friction coefficient and wear rate are dependent on the ZrB₂ content and test temperature. At a certain temperature, the friction coefficient increases with an increase in ZrB₂ content, whereas the wear rate shows a reverse trend. Due to the improvement in thermal stability and high-temperature softening resistance, the composite shows improved wear resistance and increased transition temperature from mild wear to severe wear.     

锡青铜-钢背双金属固体自润滑复合材料的摩擦性能研究

采用粉末冶金工艺制备含石墨固体润滑剂的锡青铜-钢背复合材料,研究了石墨含量对材料的硬度、显微组织和摩擦磨损性能的影响,并考察了摩擦磨损机制。结果表明:在含石墨的青铜-钢背双金属材料中,随着石墨含量的增加,材料的硬度逐渐降低,摩擦磨损性能逐渐改善,但是其显微组织的均匀性也逐渐变差;在石墨含量为3%～5%(质量分数)时,双金属材料既具有较好的摩擦磨损性能,同时表面铜合金层与钢背的黏结强度也很高;随着速度和负荷的增加,材料的摩擦因数降低,磨损增加;摩擦过程中,石墨在摩擦面上成膜是材料具有减摩自润滑性能的主要原因。     

二硫化钼填充高岭土基矿物聚合物复合材料的摩擦学性能研究

研究了MoS2填充量对高岭土基矿物聚合物复合材料的力学性能和摩擦磨损性能的影响,利用XRD、SEM分析了材料的微观结构和磨损表面形貌。结果表明,填充MoS2后矿物聚合物材料的力学性能会有一定程度的降低,但其摩擦磨损性能可以得到有效改善,当MoS2体积分数为30%时,摩擦因数和磨损率均达到最低,分别为0.423和1.23×10-4mm3/(N.m)。研究发现,当二硫化钼含量较低时,磨损机制主要是磨粒磨损;当二硫化钼含量较高时,磨损机制是磨粒磨损和粘着磨损。     

摩擦化学反应对环氧复合材料摩擦性能的影响

碳纤维和纳米粒子混杂填充环氧复合材料对其减摩耐磨性能的提高具有协同效用。为了研究其协同作用机制,用X射线光电子能谱仪(XPS)对材料摩擦前后磨损面进行分析;用与扫描电镜联用的X射线能谱仪(EDS)对摩擦后的对偶面进行分析;用纳米闪光导热仪对材料的导热系数进行分析;用热分析仪对材料磨损面热性能进行分析。结果表明,复合材料中碳纤维增加了基体的导热性,纳米粒子增强了基体的力学性能,减弱了分子链的氧化降解反应,混杂填料兼备两方面的因素且互相促进,在提高复合材料的减摩耐磨性中表现出协同效应。     

基于UHMWPE/纳米ZnO复合材料的滑动摩擦磨损机制

用热压成型法制备了超高分子量聚乙烯(UHMWPE)纳/米ZnO复合材料,采用销盘式摩擦磨损试验机考察了载荷和相对滑动线速度对复合材料摩擦学性能的影响;采用扫描电子显微镜观察了复合材料磨损表面形貌。结果表明:在低载荷试验条件下磨损机制为粘着磨损,在高载荷试验条件下磨损机制为粘着磨损和疲劳磨损。而在一定载荷试验条件下,无论相对滑动线速度高或低,复合材料的磨损机制主要表现为粘着磨损,只是在高速情况下粘着磨损程度加大,局部还出现了表面撕裂的痕迹。     

Effect of Hot Extrusion on Electrical Tribological Behavior of Ag-Cu/MoS2 Composite under Air and Vacuum Conditions

The different microstructures of silver–copper/molybdenum disulfide (Ag-Cu/MoS₂) composites were manufactured by hot press and hot extrusion processes to investigate the electrical tribological behaviors of both the hot-pressed and hot-extruded composites under air and vacuum. The results showed that microstructures and properties of Ag-Cu/MoS₂ composites were improved by hot extrusion, which decreased the wear rates rapidly in both air and vacuum. In air, hot extrusion could improve the transfer layer and tribofilm, resulting in a significant decrease in contact voltage drop, which goes from more than 70 mV in the hot-pressed composite to 30 mV at the hot-extruded composite. Under vacuum condition, some wear debris was melted on the worn surface and then transferred to the counterface to form the transfer layers, which led to the lower contact voltage drops under vacuum, about 6 mV in hot-pressed composites and 3 mV in hot-extruded composites. In addition, the severe adhesive and abrasive wear were attributed to the molten wear debris and transfer layer, resulting in a dramatic fluctuation in the friction coefficient in a vacuum.     

石墨含量对铜基滑动轴承材料摩擦特性影响的数值模拟

采用离散元软件建立了不同石墨含量铜基滑动轴承材料的数值模型,模拟了铜基复合材料与45#钢摩擦副的滑动摩擦过程,探究了石墨含量对铜基轴承材料的抗压强度和摩擦学行为的影响.结果表明:随着石墨含量的增多,材料的抗压强度持续降低;铜基石墨复合材料与45#钢滑动摩擦过程中会在45#钢表面附着转移石墨颗粒,转移石墨颗粒的形成可以有...     

水润滑下偶件表面粗糙度对PTFE复合材料摩擦学性能的影响

通过水润滑下的摩擦磨损实验,研究了偶件表面粗糙度对MoS2/PTFE复合材料摩擦学性能的影响,分析了在不同的偶件表面粗糙度下的摩擦学行为.实验结果表明:在水润滑下,一般存在着一个较佳的偶件表面粗糙度范围,在这个范围内可以取得较低的摩擦因数和磨损率;当偶件表面粗糙度高于这个范围时,摩擦磨损机制主要是机械作用;而当偶件表面粗糙度低于这个范围时,则主要是由于分子作用导致摩擦磨损.即当偶件表面粗糙度超出某一范围时,摩擦磨损行为将发生转变.     

磁性液体摩擦学性能研究

在溶液中原位合成了含磁性纳米微粒的磁性液体,利用MRH-3高速环块摩擦试验机考察了液体石蜡基磁性液体的摩擦学性能.结果表明:制备的磁性液体颗粒大小均匀, 粒径分布窄,在液体石蜡中具有良好的分散稳定性;磁性液体的减摩和抗磨能力随着其密度的增加而增加;在相同试验条件下,磁性液体比液体石蜡具有更好的减摩和抗磨性能,并具有更高的承载能力.     

填料种类对聚苯酯基复合材料摩擦学性能的影响

在聚苯酯(Ekonol)中分别添加不同种类的填料,制备出一系列性能不同的Ekonol基复合材料,研究了填料的形态、性质对Ekonol复合材料摩擦磨损性能的影响,分析了磨损面、对磨面转移膜形貌,并探讨了摩擦磨损机制。结果表明,在填料的填充量相同时,层状固体润滑剂聚四氟乙烯(PTFE),由于从本质上改善了非熔融Ekonol的内部粘结,且协助形成较为连续、平滑的转移膜,对Ekonol摩擦学性能的改善最为明显;其次为纤维状填料。相比于尺寸细微的六钛酸钾晶须,粗大的玻璃纤维(GF)或碳纤维(CF)之间相互交错,对Ekonol起到了较好的承载骨架作用,更为有效提高Ekonol的摩擦学性能。GF比CF与Ekonol之间的亲和性较好,对应于GF/Ekonol复合材料的摩擦学性能优于CF/Ekonol复合材料;纳米颗粒填料对Ekonol有着弥散增强作用,但对Ekonol摩擦学性能的改善效果最差。     

有机钼复合润滑剂在高温微动和滑动条件下的摩擦磨损行为

以矿物基650SN油作为基础油,采用复配技术制备了有机钼复合润滑剂。利用SRV微动磨损试验机和T-11滑动磨损试验机考察了该复合剂的高温摩擦学行为,采用扫描电子显微镜和X射线光电子能谱仪对其润滑下的磨痕表面形貌和表面膜的元素组成进行了分析,探讨了复合剂的减摩润滑机制。结果表明:有机钼复合剂具有良好的高温微动和滑动摩擦学行为,与基础油相比,复合剂能够使钢-钢摩擦副在高温微动和滑动过程中的摩擦因数降低28%和43%,抵抗微动和滑动磨损的能力分别提高53%和54%。这是由于有机钼复合剂通过分解、吸附和摩擦化学反应,在摩擦副金属表面形成了含磷酸盐的沉积膜和含FeS、MoS2的化学反应膜共同组成的复合边界润滑膜,从而表现出优良的减摩润滑效果。     

烧结温度对铁基粉末冶金航空刹车材料摩擦磨损性能的影响

研究了不同烧结温度(900,930,950,980,1020℃)对飞机铁基粉末冶金刹车材料材料显微组织、致密化和摩擦磨损性能的影响。借助于材料组织结构、摩擦试验后的材料表面观察及理论分析,阐述了材料组织结构及摩擦磨损变化的机制。结果表明:900℃的试样由于烧结不够充分,材料密度较低,珠光体的数量较少,硬度低,耐磨性差,经过摩擦试验后,摩擦材料表面大面积剥落和点蚀比较严重,材料磨损量较大,磨屑以大块状及条状为主;930℃试样的材料密度增加,珠光体数量增加,硬度及耐磨性增加,经摩擦试验后,试样表面比较光滑,但仍有大量的点状剥落,材料磨损量较900℃的试样有所降低;当烧结温度由950℃升高至1020℃时,由于原子扩散的加剧,材料的基体具有足够强度,珠光体的数量显著增加,显著提高了材料的耐磨性,经摩擦试验后,材料表面生成了完整的氧化膜,材料的磨损量变化不大,相对于950℃和980℃的试样而言,1020℃时的材料摩擦表面出现更少的点状脱落并形成了多层叠加的工作层。     

Dry sliding wear behaviour of polyamide 66 and polycarbonate composites

A study has been made of the reciprocating dry sliding wear behaviour of polyamide 66 and polycarbonate containing glass fibres, ultra high molecular weight polyethylene (UHMWPE) and polytetrafluoroethylene (PTFE/2% Si oil). Studies have been conducted at sliding loads of 2 kg and 10 kg at an average velocity of 0.33 m s⁻¹ against a hardened stainless steel counterface with a surface roughness of 0.3 μm.It has been shown that additions of 10–15% of filler/reinforcement lead to greatly improved sliding wear behaviour. PTFE/2% Si oil filled polyamide 66 has been shown to have the best overall wear performance whilst the high glass filled variants of polyamide 66 and polycarbonate have the best combination of wear resistance and mechanical strength. These findings are discussed with reference to composite constitution and properties, thermal effects and counterface interactions. Explanations are advanced to account for the differences in behaviour inter alia the composite materials.     

Tribological Behavior of PTFE Composites Filled with PEEK and Nano-Al2O3

In this study, the tribological properties of polytetrafluoroethylene (PTFE) composites filled with polyetheretherketone (PEEK) and nano-Al₂O₃ particles were studied using a block-on-ring wear tester. The tribological performance of the composites was affected by the experimental parameters (sliding speed, normal load, and environmental temperature) and the composites achieved a high-speed sliding friction state. The results showed that the PEEK and nano-Al₂O₃ particles significantly improved the wear resistance of the PTFE composites. In addition, the nano-Al₂O₃ particles increased the hardness of the composites and enhanced the mechanical properties to enable applications in a wider range of industrial fields. The effects of the sliding speed and normal load on the tribological properties were more significant than that of the environmental temperature. In addition, the entire wear process was divided into three stages (the initial wear stage, severe wear transition stage, and ultralow stable wear stage), according to the evolution of the tribological characteristics (wear rate, morphology of the worn surface and transfer film, and wear debris morphology).     

Effect of Copper Content on the Mechanical and Tribological Properties of ZnAl27-Based Alloys

One binary ZnAl27- and five ZnAl27-based ternary alloys containing 1–5% Cu were produced by permanent mould casting. Their friction and wear properties were examined using a block-on-ring test machine after determining their hardness and tensile strength. It was observed that the hardness and tensile strength of the ZnAl27-based ternary alloys increased with increasing copper content up to 2% due to solid-solution hardening, above which their tensile strength decreased, while hardness continued to increase. This is attributed to the formation of copper-rich and T phases, which reduce the solid-solution hardening of the alloys. It was found that the wear volume loss of the ZnAl27-based alloys decreased with increasing copper content up to 2% but showed a small increase above this level. Therefore, it was concluded that the wear resistance of ZnAl27-based alloys containing 1 to 5% Cu correlates well with their tensile strength. In addition, smearing and scratches were found to be the main features of the wear surfaces of the ZnAl27-based alloys under static loading and lubricated sliding conditions.     

基体成分对Fe_3Al基复合材料摩擦学性能的影响

采用热压烧结法制备一种新型Fe3A l基复合材料,讨论基体成分对其摩擦学性能的影响。研究结果表明:本实验中,Fe3A l粉体的最佳球磨时间为60 h;随着A l含量提高,Fe3A l基复合材料的摩擦因数略有降低但耐磨性明显提高,合金元素Cr的加入有效地改善了材料的摩擦学性能,以Fe-28A l作为摩擦材料的基体即可很好地满足性能要求;Cu作为基体中的软相,摩擦因数随游离Cu含量的增加呈上升趋势但摩擦稳定性变差,且耐磨性降低,Cu含量的最佳范围为12%~18%(质量分数),随着石墨含量的增加,材料的摩擦因数和磨损率都下降,但石墨含量过高会导致材料性能恶化,石墨的最佳含量为8%~12%(质量分数)。     

Study on Tribological Performance of NiAl Matrix Self-Lubricating Composites Containing Graphene at Different Loads

This study aimed to explore the possibility of improving the tribological performance of NiAl matrix composites by graphene addition. Friction and wear experiments of as-prepared specimens were conducted under different conditions using a pin-on-disk wear testing machine. NiAl matrix composites containing graphene showed satisfactory performance in friction coefficient and wear resistance compared to NiAl matrix composites without graphene. For the active effect of graphene, the friction coefficient and wear rate of NiAl matrix composites were maintained at relatively lower values. The beneficial antifriction and antiwear effects of graphene gradually failed when the applied load was above 8 N. Graphene in NiAl matrix composites played an active role in the formation of a friction layer, which was beneficial to the lower friction coefficient and wear rate. In light of this research, graphene plays an active role in reducing the friction coefficient and wear rate. Hence, graphene has great potential in applications as an effective solid lubricant to promote tribological behavior.     

聚合物复合材料自润滑体系内外因素的摩擦学相互作用

从聚合物基复合材料在不同无润滑工况下的设计角度,讨论了高温、高压、高速、对偶、气体介质等外部因素对不同材料摩擦磨损性能的影响,分析了摩擦磨损机制,分析得出:由于填料、聚合物基体、对偶、工作介质之间存在着复杂的非线性相互作用,摩擦化学反应的程度与类型不同,不同填料填充聚合物基复合材料都有各自适用的摩擦系统,没有任何一种材料能适用于所有摩擦系统;指出目前摩擦学理论多建立在常温低压低速体系下,这与工程应用实际相脱节,对于复合材料在极端工况下的摩擦学机制、内外因素相互作用的研究,还有待进一步深入展开。     

铁基粉末冶金材料的高速干切削试验研究

用陶瓷刀具、涂层刀具和硬质合金刀具进行了铁基粉末冶金零件的干切削对比试验,研究了切削速度、切削深度以及进给速度与刀具耐用度和加工表面粗糙度的关系,分析了陶瓷刀具的磨损机理。结果表明所选用陶瓷刀具的切削性能明显优于涂层刀具和硬质合金刀具;陶瓷刀具前刀面主要磨损形式为月牙洼磨损与剥落,后刀面的主要磨损原因为磨粒磨损;认为陶瓷刀具更适合用于粉末冶金零件的切削加工。     

Effect of phosphide and matrix microstructures on the dry sliding wear of grey cast iron

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.