Friction and Wear Properties of TiAl-Ti3SiC2-MoS2 Composites Prepared by Spark Plasma Sintering

TiAl matrix self-lubricating composites (TMC) with various weight percentages of Ti₃SiC₂ and MoS₂ lubricants were prepared by spark plasma sintering (SPS). The dry sliding tribological behaviors of TMC against an Si₃N₄ ceramic ball at room temperature were investigated through the determination of friction coefficients and wear rates and the analysis of the morphologies and compositions of wear debris, worn surfaces of TMC, and the Si₃N₄ ceramic ball. The results indicated that TMC with 10 wt% (Ti₃SiC₂-MoS₂) lubricants had good tribological properties due to the unique stratification subsurface microstructure of the worn surface. The friction coefficient was about 0.57, and the wear rate was 4.22 × 10^?4 mm³ (Nm)^?1. The main wear mechanisms of TMC with 10 wt% (Ti₃SiC₂-MoS₂) lubricants were abrasive wear, oxidation wear, and delamination of the friction layer. However, the main wear mechanisms of TMC without Ti₃SiC₂ and MoS₂ lubricants were abrasive wear and oxidation wear. The continuous friction layer was not formed on the worn surfaces. The self-lubricating friction layer on the frictional surface, different phase compositions and hardness, as well as density of TMC contributed to the change in the friction coefficient and wear rate.     

A Model for Polymer Composite Wear Behavior Including Preferential Load Support and Surface Accumulation of Filler Particulates

A rule-of-mixtures model is developed for the time-dependent wear and friction behavior of polymer matrix materials containing particulate filler inclusions, based upon the specific wear rates of filler and matrix materials. The model accounts for the accumulation of wear-resistant filler particles within the near-surface region of the composite as sliding proceeds. Account is also made for preferential support of the normal load by filler particles at the sliding surface. Though particle/matrix interfacial shear stress and particle aspect ratio do affect initial transient behavior, wear rate, and friction are independent of preferential load support under steady-state conditions. The model indicates that steady-state composite wear rate can be most affected by the specific wear resistance of the filler particles, as well as the volume fraction filling of particles into the polymer matrix.     

Formation of Friction Layers in Graphene-Reinforced TiAl Matrix Self-Lubricating Composites

The friction layer structure has been proved to be formed during severe plastic deformation and markedly improves the tribological properties of material. The dry friction and wear performance of graphene-reinforced TiAl matrix self-lubricating composites (GTMSC) at different sliding velocities are systematically researched. GTMSC show the best tribological properties and special friction layer structure containing a wear-induced layer and a grain refinement layer with a nanocrystalline (NC) structure under surface after sliding at a sliding speed of 1.1 m/s. Nanoindentation results show that the grain refinement layer has a higher hardness and elastic modulus than the wear-induced layer. This special microstructure of friction layers beneath the surface after sliding leads to a low coefficient of friction and high wear resistance of GTMSC. Moreover, it is deduced that the appearance of an NC structure results in hardening of the material. The formation mechanisms of friction layers are researched in detail. It can be concluded that the formation of a wear-induced layer results from frictional heat and fracture of the counterpart. The formation of a grain refinement layer is due to severe plastic deformation and dynamic recrystallization. Severe plastic deformation results in the formation of an NC structure and dynamic recrystallization leads to grain refinement.     

Tribological Behavior of Novel Ti3SiC2 (Natural Nanolaminates)-Reinforced Epoxy Composites during Dry Sliding

In this article, we report for the first time the synthesis and characterization of Ti₃SiC₂–epoxy (MAXPOL) composites. Three novel composites were designed by adding 20.7, 30.6, and 71.6 vol% Ti₃SiC₂ particulates to an epoxy matrix. The microstructure evaluation by scanning electron microscopy (SEM) showed that the Ti₃SiC₂ particles are well dispersed in the epoxy matrix. The addition of Ti₃SiC₂ enhanced the ultimate yield strength (UYS) and hardness of all of the composites compared to epoxy. Tribological studies were performed by a tab-on-disc method against Inconel 718 and alumina substrates. In both cases, the mean friction coefficient (µ_mean) decreased as the concentration of Ti₃SiC₂ in the epoxy matrix was increased. The concomitant wear rates (WRs) also decreased steadily and then increased slightly after reaching a concentration of ~32.6 vol% Ti₃SiC₂. The tribological studies proved conclusively that the addition of Ti₃SiC₂ in the epoxy matrix imparts self-lubricity to the composites. The tribofilms formed on different tribosurfaces were also characterized by detailed SEM investigations.     

硼酸的纳米摩擦学研究

本文以原子力显微镜为工具,对不同湿度环境下氧化硼表面上形成的硼酸进行研究,初步揭示了其纳米摩擦学特性。     

Effect of Al2O3 Particle Size on Electrical Wear Performance of Al2O3/Cu Composites

Al₂O₃/Cu composites (1.0 vol%) reinforced with different size of α-Al₂O₃ particles were fabricated by a powder metallurgy method and electrical sliding wear tests were performed on a self-made pin-on-disk electrical wear tester. The effect of Al₂O₃ particle size on electrical wear performance of the Al₂O₃/Cu composite was studied, and the wear mechanism of the Al₂O₃/Cu composite was also discussed based on worn surface observations. The results show that the tribological properties of A1₂O₃/Cu composite are closely related to the mechanical properties. With an increase in Al₂O₃ particle size, the wear rates of A1₂O₃/Cu composites have a reverse variation with hardness of A1₂O₃/Cu composites. In the range of 50–100 nm, Al₂O₃/Cu composites have the highest wear resistance and mechanical properties. Microstructural observation revealed that the wear mechanisms of Al₂O₃/Cu composites were mainly adhesive wear and plastic deformation accompanied by a small amount of arc damage. In addition, the plastic deformation area on the pin sample of the frictional end depends on the electrical wear resistance of A1₂O₃/Cu composites.     

Role of Al2O3 in Semi-Metallic Friction Materials and its Effects on Friction and Wear Performance

In this work the semi-metallic friction composites with moderately increased content of Al₂O₃ (0, 3.4, 5.6, 9.0, and 14.6 vol%) were successfully fabricated by casting technology and their tribological properties were evaluated. The character of friction surfaces was confirmed by SEM. The sample with 5.6 vol% of Al₂O₃ offers the best tribological property among the prepared formulations, and is characterized by high and steady friction coefficient (about 0.45) and low wear. With the temperature increasing, the stibnite patches population on friction surface increases and individual steel fibers spread due to their plastic deformation to form larger primary contact plateaus. The area covered by contact primary plateaus decreases with the alumina content increasing.     

Al2O3纤维填充PTFE复合材料摩擦磨损性能分析

利用M-200型摩擦磨损试验机考察了填料含量及载荷对粉状Al2O3纤维填充PTFE复合材料摩擦磨损性能的影响，采用扫描电子显微镜观察分析磨损表面形貌及磨损机理。结果表明：Al2O3纤维填料可提高PTFE的硬度，从而可提高PTFE的耐磨性，但复合材料中Al2O3含量较高时会导致磨粒磨损，且AL2O3含量越高相应的磨粒磨损越严重。在本试验条件下，当Al2O3的质量分数为20%左右时，PTFE复合材料的耐磨性最佳；PTFE复合材料同钢对磨时的摩擦系数比纯PTFE大，且随Al2O3含量的增加而增大。     

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).     

Ti-Al/TiC+Al2O3复合材料的制备与性能

用机械合金化和热压烧结制备了Ti-Al/TiC+Al2O3复合材料.研究了不同烧结温度(1550、1650℃)和热处理温度(700、900℃)对烧结体的力学性能和显微组织的影响.结果表明烧结体具有良好的力学性能,硬度达到92 HRA,抗弯强度可大于600MPa,而断裂韧度最高可达8.021 MPa·m1/2.     

Ti-Al/TiC+Al2O3复合材料的制备与性能

用机械合金化和热压烧结制备了Ti-Al/TiC+Al2O3复合材料.研究了不同烧结温度(1550、1650℃)和热处理温度(700、900℃)对烧结体的力学性能和显微组织的影响.结果表明:烧结体具有良好的力学性能,硬度达到92 HRA,抗弯强度可大于600MPa,而断裂韧度最高可达8.021 MPa·m1/2.     

直接金属氧化法制备SiCp/Al2O3-Al复合材料

利用直接金属氧化法制备了SiC颗粒增强Al2O3-Al基复合材料，借助于XRD和光学显微镜对该复合材料的组成及微观结构进行了观察，分析了SiO2层、合金成分和制备温度对复合材料性能的影响。结果表明：该复合材料结构致密且渗透完全，微观结构由三种相互穿插相组成：SiC预制体、连续的Al2O3基体及呈网状结构分布的未被氧化的残余铝合金。     

硼酸酯的在线强化性能及机理研究

研究了硼酸三丙酯的摩擦表面在线强化性能．结果表明，硼酸三丙酯具有较好的摩擦表面在线强化功能；动态质谱分析给出了硼酸酯在摩擦界面发生的反应。     

Synergetic Effect of Lubricant Additive and Reinforcement Additive on the Tribological Behaviors of PEEK-Based Composites under Seawater Lubrication

Polyetheretherketone (PEEK)-based composites reinforced with lubricant additive (polytetrafluoroethylene, PTFE) and reinforcement additives including carbon fiber (CF), glass fiber (GF), and bronze powder were prepared using a hot-press molding technique. The synergetic effects of different additives on the tribological behaviors of PEEK-based composites sliding against 316 steel under seawater lubrication were investigated systematically using a ring-on-block test rig. The results showed that lubricant additive PTFE can decrease the friction coefficient and consequently improved the wear resistance of PEEK under seawater lubrication, especially when the volume fraction of PTFE was about 20%. It was also found that the incorporation of CF can further improve the wear resistance of PEEK blended with 20% PTFE, especially under high load and high sliding speed. This suggested that a synergistic effect on improving the wear resistance of PEEK existed between PTFE and CF, which originated from good lubrication of PTFE, good reinforcement of CF, and good interfacial combination between CF and PEEK-20%PTFE. However, two other reinforcement additives of GF and bronze powder had an antagonistic effect but not a synergetic effect with PTFE; that is, the incorporation of the two additives greatly deteriorated the wear resistance of PEEK blended with 20% PTFE.     

钴包覆纳米Al2O3/TiCp复相陶瓷的力学性能及其增韧机制

利用钴包覆的纳米Al2O3和TiC粉料采用热压烧结法制备了抗弯强度为782MPa、断裂韧度为7.81MPa·m 1/2的复相陶瓷材料,并建立了该种材料的显微结构示意图,从界面的角度分析了力学性能提高的原因.观察材料的断口形貌发现形成了晶内型结构,并观察到了裂纹的扩展路径以及裂纹的分叉、偏转、桥联等现象.     

氧化铝晶须增强铝基复合材料的应用前景

介绍了晶须的性质及铝基复合材料的性能特点,概述了国内外研究现状,提出了用水热法制备三氧化二铝晶须的新思路,分析了氧化铝晶须增强铝基的应用前景.阐明了开发氧化铝晶须的意义.     

Al_2O_3连续增强铝基复合材料的干摩擦磨损特性

通过摩擦磨损试验对比研究了含质量分数18%SiC颗粒和不含SiC颗粒的Al2O3连续增强铝基复合材料与NAO(无石棉有机材料)配副的干滑动摩擦磨损行为。结果表明:复合材料在较低的滑动速度(0.628m·s-1)下,最大启动摩擦因数随正压力的增大而降低;在较高的滑动速度(2.512m·s-1)下,最大启动摩擦因数随正压力的增大呈先减小后增大的趋势;正压力一定时,最大启动摩擦因数随滑动速度的增大先减小后增大;含SiC的Al2O3连续增强铝基复合材料比不含SiC的Al2O3连续增强铝基复合材料具有更高的摩擦因数和更好的耐磨性。     

钴包覆纳米Al2O3/TiCp复相陶瓷的力学性能及其增韧机制

利用钴包覆的纳米Al2O3和TiC粉料采用热压烧结法制备了抗弯强度为782MPa、断裂韧度为7.81MPa·m 1/2的复相陶瓷材料,并建立了该种材料的显微结构示意图,从界面的角度分析了力学性能提高的原因.观察材料的断口形貌发现形成了晶内型结构,并观察到了裂纹的扩展路径以及裂纹的分叉、偏转、桥联等现象.     

显微结构对Y-TZP/Al2O3复合陶瓷磨料磨损性能的影响

以不同Y2O3加入方式(如化学共沉淀和机械混合)制备的Al2O3增强Y-TZP陶瓷(AZD)为研究对象，研究了显微结构对陶瓷耐磨性的影响。结果表明：化学共沉淀法制备的CYADZ与机械混合的MYADZ的硬度和断裂韧性值相近：CYADZ结构均匀、品粒细小，而由于Y2O3的不均分布，MYADZ结构不均、晶粒相差较大。球磨磨料磨损后，CYADZ复合陶瓷较MYADZ复合陶瓷耐磨性好，宏观力学性能如硬度和断裂韧性对陶瓷材料耐磨性的影响应以显微结构为先决条件。     

Tribological Behavior of Si3N4-hBN Ceramic Materials without Lubrication under Different Test Modes

Unlubricated tribological behaviors of silicon nitride–boron nitride (Si ₃ N ₄ -hBN) composites were investigated with two test modes in air by using a pin-on-disc tribometer. Under upper-disc-on-bottom-pin test mode, the addition of hBN to Si ₃ N ₄ resulted in a significant decrease of the friction coefficient, from 0.54 for Si ₃ N ₄ against Si ₃ N ₄ to 0.19 for Si ₃ N ₄ -20% hBN against Si ₃ N ₄ . The surface analysis indicated that a tribochemical film consisting of SiO₂ and H ₃ BO ₃ was formed on the wear surfaces. The formation of tribochemical film might be attributed to the embedment of wear debris into the spalling pits on the wear surfaces of Si ₃ N ₄ -hBN specimen. The wear debris reacted with moisture in air, and the resultant tribochemical film lubricated the wear surfaces. Under upper-pin-on-bottom-disc test mode, the wear mechanism was dominated by abrasive wear, and no tribochemical products could be detected on the wear surfaces. A slight decrease of the friction coefficient, from 0.85 for Si ₃ N ₄ /Si ₃ N ₄ to 0.56 for Si ₃ N ₄ /Si ₃ N ₄ -30% hBN, was obtained, which might be attributed to the layered structure of hBN.