聚酰亚胺/聚全氟乙丙烯层压复合材料摩擦性能研究

用热压法制备了聚酰亚胺/聚全氟乙丙烯层压复合材料.用磨损试验机在不同滑动速率、负载下研究了其摩擦学性能.对不同负载、滑动速率下的摩擦系数随时间的变化进行了详细分析.用扫描电子显微镜观测了试样的磨损面并分析了其摩擦机理.实验结果表明,该材料具有优良的摩擦学性能并且磨合时间很短.摩擦系数随时间变化,并且与负载和滑动速率有关...     

Wear and friction properties of spark plasma sintered SiC/Cu nanocomposites

In this study, in order to determine the effect of SiC nanoparticles on tribological properties of nanostructured copper, the dry sliding wear and friction behaviors of nanostructured copper and copper reinforced with silicon carbide nanoparticles, produced by high energy ball milling and spark plasma sintering, were investigated by using an oscillating friction and wear tester under different normal loads. To determine the dominant wear mechanism, the worn surfaces and obtained debris after wear tests were analyzed by scanning electron microscope (SEM). The results showed that the addition of 4 vol% silicon carbide to copper matrix reduced the wear track depth and the coefficient of friction. Investigation of the worn surfaces revealed that SiC nanoparticles on the top of worn surface decreases the plastic deformation in subsurface region and alleviate severe wear. Lower plastic deformation during dry sliding wear test was attributed to high hardness of the nanocomposite that has been resulted from grain growth inhibiting and reinforcing effects of the nanoparticles. Plastic deformation and delamination were determined as major wear mechanisms in both materials.     

Temperature Dependence of Diamondlike Carbon Film Tribological Characteristics

The tribological characteristics of a diamondlike carbon (DLC) film deposited on high-speed steel were investigated systematically by using a ball-on-flat reciprocating tribometer over a range of temperatures (from −40° to 20°C). The results indicated that the temperature dependence of the DLC film's tribological behavior was associated with the counterpart material. DLC presented favorable tribological behavior while sliding on itself. However, when a steel ball slides against the DLC film, there is evidence that the heat generated has a significant impact on friction and wear. Microanalysis of wear tracks on the films showed that multiple wear mechanisms took place during testing. At higher temperatures, material transfer dominated the wear behavior, while fatigue-induced microcracking was the predominant wear mechanism at low temperatures. Raman analysis indicated that the DLC film was mechanically worn rather than removed by tribochemical interactions between the friction pairs.     

The effect of residual stresses in functionally graded alumina–ZTA composites on their wear and friction behaviour

In this work we have evaluated the effect of compressive stress levels in functionally graded alumina–ZTA composites on their wear and friction behaviour during sliding in water. Neutron diffraction, X-ray diffraction and scanning electron microscopy were employed to analyze the samples and assess the acting tribological mechanisms. The results, which are compared to results from homogeneous alumina, show that with increasing residual compressive stresses in the samples of functionally graded material (FGM) both the wear and the friction are reduced. As a consequence of reduced crack formation and debris detachment from the surface (due to increased residual compressive stress) the tribochemical layer became thinner, with fewer topographical irregularities at the surface. This increases the role of the tribochemical actions compared to the mechanical wear, which beneficially affects the tribological performance in water.     

High-temperature compressive properties and tribological behaviour of Mo2NiB2–Ni cermets

The present work investigated the high-temperature compressive strength and tribological behaviours of Mo₂NiB₂–Ni cermets from 25 to 900 °C. Mo₂NiB₂–Ni cermets with four different Ni additions were first fabricated successfully and then tested. The results show that cermets with Ni/B 1.1 have the best compressive strength of 531.8 MPa at 900 °C and superior strength retention at high temperature. With the best high-temperature compressive strength, Mo₂NiB₂–Ni cermets with Ni/B 1.1 are used as pins with Si₃N₄ disks in a tribological test. The wear rate of Mo₂NiB₂–Ni cermets gradually increases as the temperature increases from 25 to 900 °C, while the friction coefficient shows the opposite trend. Within the entire testing temperature range, the friction coefficient decreases, and the minimum friction coefficient is obtained at 900 °C. The decline of the friction coefficient is attributed to the self-lubricating oxidation tribolayer covering the worn surface. Moreover, the dominant wear mechanism changes from abrasive wear to oxidation wear as the temperature exceeds 600 °C.     

Tribological Characteristics of SiC Ceramics in High-Temperature and High-Pressure Water

The effects of temperature and sliding speed on the tribological behavior of a SiC ceramic by sliding on the same material in deoxygenated water were investigated from room temperature to 300°C under the corresponding saturated vapor pressures. The friction coefficient and specific wear rates of both plates and disks increased at elevated temperatures at all sliding speeds, but decreased with increasing sliding speed at 120° and 300°C. Fine mirrorlike worn surfaces were observed without wear debris under all sliding conditions. The wear mechanism appears to consist of hydrothermal oxidation of SiC and dissolution of reaction products such as silica.     

Mechanical and tribological properties of glass–epoxy composites with and without graphite particulate filler

The objectives of this research article is to evaluate the mechanical and tribological properties of glass‐fiber‐reinforced epoxy (G–E) composites with and without graphite particulate filler. The laminates were fabricated by a dry hand layup technique. The mechanical properties, including tensile strength, tensile modulus, elongation at break, and surface hardness, were investigated in accordance with ASTM standards. From the experimental investigation, we found that the tensile strength and dimensional stability of the G–E composite increased with increasing graphite content. The effect of filler content (0–7.5 wt %) and sliding distance on the friction and wear behavior of the graphite‐filled G–E composite systems were studied. Also, conventional weighing, determination of the coefficient of friction, and examination of the worn surface morphological features by scanning electron microscopy (SEM) were done. A marginal increase in the coefficient of friction with sliding distance for the unfilled composites was noticed, but a slight reduction was noticed for the graphite‐filled composites. The 7.5% graphite‐filled G–E composite showed a lower friction coefficient for the sliding distances used. The wear loss of the composites decreased with increasing weight fraction of graphite filler and increased with increasing sliding distance. Failure mechanisms of the worn surfaces of the filled composites were established with SEM. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2472–2480, 2007     

Friction and Wear of Woodceramics under Oil and Water Lubricated Sliding Contacts

Friction and wear properties of woodceramics were evaluated under oil and water lubricated sliding contacts. The experiment was conducted with a block on a ring wear tester. The block material was woodceramics (MDF-800) and and the ring was a forging steel (SF55). The sliding velocity and the load were varied in the ranges 1.0–19.0 m/s and 98–294 N, respectively. The ring temperature was measured using a thermocouple located at 1.0 mm below the frictional surface of the ring.In the oil lubrication, the coefficient of friction was small and constant at 0.12, irrespective of the sliding velocity. The specific wear rate of the woodceramics was also small and was in the range 5 × 10–7–2 × 10–6 mm3/Nm. With the increase in the load, the coefficient of friction and the specific wear rate of woodceramics decreased. It was found that low friction and low wear could be maintained at least until a ring temperature of 160°C.In the water lubrication, the coefficient of friction was small and constant at 0.16 until the sliding velocity of 12 m/s. The specific wear rate was also small and was in the range 3 × 10–7–2 × 10–6 mm3/Nm. As the sliding velocity increased further and the ring temperature became high, friction and wear increased.     

Influence of the Composition of Carbon-fiber Phenolformaldehyde Composite Materials on Their Tribological Characteristics

Abstract

Carbon-fiber phenolformaldehyde composite materials have been obtained by two technological methods—prepreg and dry mixing of components. The tribological properties of the composite materials are investigated. As such tribological characteristics are used friction factor and the intensity of wear as a criterion for the wear stability of the material. Influence of some dispersion fillers-bentonite clay, talc, kaolin and boron carbide is investigated to the tribological characteristics. The influence of loading and the speed of sliding over the friction factor and the wear hardness is determined too.

The tribological properties of the obtained composite materials help them join the best materials working in conditions of dry friction and ensure manufacturability of their obtaining and processing and high reliability in operation.     

Self-lubricating behavior caused by tribo-oxidation of Ti3SiC2/Cu composites in a wide temperature range

Ti₃SiC₂/Cu composite, a new wide temperature range intelligent lubricating functional material, was fulfilled, for mechanical equipment components, by Spark Plasma Sintering process. The microstructure, composition and mechanical properties of the Ti₃SiC₂/Cu composites (TSC-Cu) were investigated. Additionally, the friction and wear behaviors of TSC-Cu sliding against Inconel 718 were conducted on a pin-on-disk configuration at a sliding speed of 0.5 m/s under a load of 5 N at 25–800 °C. For comparison, the tribological property of polycrystalline Ti₃SiC₂/Inconel 718 was measured in an identical condition. The worn surface of TSC-Cu was analyzed by SEM, EDS and XPS, respectively. The results indicated that TSC-Cu consisted of Ti₃SiC₂, TiC and Cu₃Si. It was worth noting that the as-formed Cu₃Si uniformly distributed along the grain boundary of Ti₃SiC₂. As for mechanical property, the addition of Cu increased the hardness, compressive strength of TSC-Cu but lowered its flexural strength. Compared with polycrystalline Ti₃SiC₂, the average friction coefficient of TSC-Cu was higher at 25–400 °C whereas it was lower at 600 °C and 800 °C. The lower friction coefficient was owing to the cooperative lubricating characteristic of tribo-oxidation films containing TiO₂, SiO₂ and CuO. Furthermore, the wear rate of TSC-Cu was absolutely lower than that of polycrystalline Ti₃SiC₂, which resulted from the effective surface strengthening effect of the as-formed hard TiC product. Moreover, the wear mechanism of the composite changed from three-body abrasion wear to adhesion wear and tribo-oxidation wear, with the temperature increasing from RT to 800 °C.     

Wear behavior of graphene/alumina composite

In the present work, the dry sliding behavior of a graphene/alumina composite material was studied against alumina in air. The tests were carried out in a reciprocating wear tester with an applied load of 20 N, a sliding speed of 0.06 m s⁻¹ and a sliding distance of up to 10 km. Under the testing conditions, the graphene/ceramic composite showed approximately half the wear rate and a 10% lower friction coefficient than the monolithic alumina. It has been found that this behavior is related to the presence of graphene platelets adhered to the surface of friction that form a self-lubricating layer which provides enough lubrication in order to reduce both wear rate and friction coefficient, as compared to the alumina/alumina tribological system.     

Effect of structure of carbon films on their tribological properties

A comparative study of the tribological properties of a library of different carbon forms is presented. The library includes hydrogen free and hydrogenated carbon films with different bonding (CC, CH, different sp³ fractions) and structure configurations (amorphous, graphitic) leading to a wide range of densities and hardness. Reference samples (Si substrates, thermally evaporated amorphous carbon, graphitic foil) were studied as well. The tribological properties were measured using a reciprocal sliding tribometer under humid (50% RH) and dry (5% RH) air conditions. Friction coefficients were measured versus the number of sliding cycles and the wear was studied using optical profilometry and imaging as well as SEM.The friction and wear performance of the carbon films were found to depend on both the structure and the ambient conditions. Hydrogen free films have friction coefficients < 0.1 for 80% sp³ bonded films and > 0.1 for 100% sp² bonded films. The wear resistance of the hydrogen free films (much larger for sp³ bonded films) significantly decreases under dry conditions. In contrast, hydrogenated films show reduction in friction with decreasing humidity (from 0.2 under 50% RH to < 0.1 under 5% RH). The wear resistance of hydrogenated films is larger for dry and smaller for humid conditions.     

水润滑下纳米三氧化二铝/端异氰酸酯基聚丁二烯液体橡胶-环氧树脂复合材料的摩擦性能

研究了纳米Al2O3/端异氰酸酯基聚丁二烯液体橡胶-环氧树脂(ETPB)复合材料在水润滑条件下的摩擦性能,并用扫描电子显微镜表征了复合材料的磨损表面形貌,探讨了磨损机理。结果表明,在水润滑条件下,纳米Al2O3/ETPB复合材料的磨损率和摩擦系数低于ETPB;载荷和滑动速率的变化对纳米Al2O3/ETPB复合材料的磨损率、摩擦系数及磨损表面形貌影响不大,复合材料的磨损表面均未产生裂纹;ETPB的磨损机理为疲劳磨损,纳米AlO/ETPB复合材料的磨损机理为机械抛光磨损。     

Effect of hBN addition on the fabrication,mechanical and tribological properties of Sialon materials

This work aims to investigate the effect of hBN on the friction and wear resistance of Sialon composite. Sialon and its composite with 10 wt% hBN were fabricated by SPS sintering. The effect of hBN additive on the phase composition, microstructure, densification behavior, mechanical and dry sliding tribological properties of Sialon material was studied. Being sintered at 1600 °C for 10 min, compared to monolithic Sialon, Sialon-hBN composite has more refined β-Sialon grains with smaller aspect ratios and slightly declined relative density. The hardness of the Sialon-hBN composite was reduced due to the weak bonding between Sialon and hBN grains. Nevertheless, its fracture toughness increased ascribing to the toughening mechanisms, including crack deflection and crack bridging. hBN had an essential impact on the tribological performances of the composite due to its lower friction coefficient and good lubrication action. Under the same densification level (i.e., with a relative density of around 97.5%), the friction and wear resistance of Sialon-hBN composite were much better than monolithic Sialon. The main wear mechanisms were tribolayer formation, oxidized wear, and abrasive wear.     

The Effect of Phase Structure on the Tribological Properties of PA66/HDPE Blends

Summary: In this paper, immiscible, partially miscible and miscible blends of polyamide 66 (PA66) and high density polyethylene (HDPE) were obtained by changing compatibilizer concentrations. Mechanical and tribological properties of materials were tested. It was found that the addition of compatibilizer greatly improved the mechanical properties of PA66/HDPE blends. The wear of PA66/HDPE blends was strongly affected by the phase structure. The best blend for lower friction coefficient and higher wear resistance was the blend with a miscible structure, which significantly improved the tribological properties of PA66 and HDPE. SEM investigations on the worn surface and the steel counterface indicated that, for the immiscible and partially miscible blend systems, the dispersed HDPE particles were pulled out from the worn surfaces during sliding because of the poor adhesion between HDPE and PA66, while this was not observed in the miscible blend system.

SEM micrograph of the worn surface formed by PA66/HDPE blend without HDPE‐g‐MAH.     

致密工艺对C/C复合材料摩擦性能的影响

采用针刺全炭纤维网胎无纬布整体结构预制体为骨架，经化学气相沉积（CVD）、树脂浸溃（RD固化致密及炭化、石墨化制得C／C复合材料。研究了粗糙层（RL）和树脂炭（RC）对摩擦性能的影响。结果表明，RL结构的C／C复合材料的摩擦性能较好，稳定性较高，是用作飞机刹车材料的前提；采用CVD＋RI制备且石墨化后的C／C复合材料具有优良的摩擦磨损特性；CVD试样的密度较低时，摩擦系数较高，但磨损较大，较难形成完整的摩擦膜。     

Effect of densification parameters on the low-energy tribological behavior of carbon/carbon composites

The low-energy tribological behavior was investigated in carbon/carbon composites fabricated by processing with different densification parameters. In the densification process, different impregnating precursors and carbonization temperatures were used to investigate the influence on physical and mechanical properties, microstructure and tribological behavior. Experimental results indicate that the density and hardness of resin-based specimens are higher than those of pitch-based specimens after four densification cycles. When increasing carbonization temperature in the specimens based on coal tar pitch, the open porosity increases whereas both the bulk density and the hardness decrease. When comparing the tribological properties of the specimens with different impregnating precursors, coal tar pitch specimens show lower and more stable friction coefficients and exhibit lower weight losses. This is because the pitch matrix is transferred to the preferred orientation structure carbon after carbonization. The different carbonization temperatures do influence the tribological properties; specimens carbonized at 700 °C exhibit the lowest weight loss and the most stable friction coefficient.     

Reciprocal dry sliding wear of SiCp/Al–7Si-0.3 Mg functionally graded composites: Influence of T6 treatment and process parameters

The present work discusses an attempt to enhance the mechanical and reciprocal wear response of Al–7Si-0.3 Mg alloy through the addition of 10 wt% SiC as reinforcement and subsequent T6 treatment. Friction and reciprocating wear behavior of both untreated and heat treated functionally graded composites were studied under unlubricated sliding conditions, employing a linear reciprocating pin-on-plate system over a range of applied load (10–50 N) and sliding distance (500–2500 m). Microstructural studies revealed reinforcement particle gradation across the cast thickness for untreated composite with minimal particle clusters whereas, heat treated composite showed the presence of fine α-spheroidised eutectic silicon. The outer layer of heat-treated composite when compared to outer layer of as-cast composite, revealed an 18 % increase in hardness, 70 % increase in tensile strength and 8 % decrease in wear rate. Wear studies confirmed a linear dependency between wear rate and applied load whereas, coefficient of friction displayed fluctuating trends. Wear mechanisms were identified, with worn morphology and EDS analyses in agreement with the results obtained and was correlated with the observed metallurgy and mechanical properties. These composites were identified as potential candidates for applications such as brake drums/rotors, cylinder liners, cylinder blocks and pistons.     

石墨的取向对聚酰亚胺摩擦性能的影响

通过热模压成型工艺制备了聚酰亚胺(PI)/石墨(NG)复合材料,对其摩擦性能、断面及磨痕形貌进行了测试与表征。结果表明,NG在PI基体中沿着与成型压力垂直的方向取向;当载荷不变且滑动速度较低时,垂直于摩擦面的NG比平行于摩擦面的NG更能降低PI的摩擦因数;随着滑动速度的提高,这种情况发生转变,而提高载荷后,转变点向低速移动;对比摩擦性能与磨痕形貌的结果发现二者存在紧密的联系,磨痕的表面越光滑、粗糙度越低,摩擦因数与磨损率也越低。     

纳米颗粒增强摩擦材料摩擦学性能研究

以丁腈橡胶改性酚醛树脂为基体,芳纶纤维、玻璃纤维为增强纤维,选用不同类型的纳米颗粒作为填料设计摩擦材料组分配比,并通过热压烧结制备摩擦材料。通过摩擦磨损试验机测试其在干摩擦条件下的摩擦学性能,并用扫描电镜(SEM)对材料的磨损形貌进行观察分析,以研究不同类型的纳米颗粒对摩擦材料性能的影响。研究表明:在干摩擦条件下,经过纳米颗粒改性的摩擦材料摩擦系数、硬度比未改性的材料有不同程度的提高,同时磨损率有很大程度的降低;纳米颗粒改性的摩擦材料摩擦系数、磨损率变化趋势具有一致性,均随着实验载荷、滑动速度的增大而逐渐减小;纳米颗粒改性后的摩擦材料磨损机理表现为疲劳磨损与磨粒磨损并存,而未改性的材料磨损机理主要表现为疲劳磨损。