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The glass fiber fabric reinforced polytetrafluoroethylene (GF/PTFE) self-lubricating composite was investigated by using a high frequency and high load oscillating friction and wear tester MYB-500 to carry on a whole life wear test. The self-lubricating performance and damage characteristics were studied, and the wear debris and wear surface were analyzed by microscopic detection method to discuss the key factors affecting the self-lubricating stability and service life of material. Results show that the life cycle of GF/PTFE self-lubricating composite exhibits an obvious stage characteristics, and can be divided into three stages, including running-in, stable stage and failure stage based on the change of friction coefficient and wear depth. Real-time monitoring of friction coefficient and friction temperature can effectively reflect the self-lubricating performance and life stage of the material. The change of wear depth and wear surface analysis show that the wear exhibits notable non-uniformity. According to wear mechanism, the inhomogeneity of the initial thickness of the material has a significant influence on the inconsistency of the damage during the wear process as well as its life. Therefore, by improving the curing process, the stable stage in life cycle can be prolonged and the service life of the material can also be increased.

Corrugated damage to bearings is a common fault in electrical facilities such as new energy vehicles, wind power, and high-speed railways. The aim of this article is to reveal the microscopic characteristics and formation mechanism of such damages. The corrugation with alternating "light" and "dark" shape was produced on GCr15 bearing races in the experimental conditions. Compared to the light area, the dark area (in the images generated by optical microscope) has more severe electrical erosion, lower hardness, more concave morphology, and lower oxidation. As the voltage increases, the width of the corrugation, the height difference between corrugation, and surface roughness all increase. It is believed that the formation of corrugated damage requires a sufficiently high voltage to induce the periodic destruction and reconstruction of the lubrication film. When the bearing is in a metal-lubrication film–metal contact state, the high voltage causes the lubrication film to break down and induce electrical erosion. Then, the contact area is in metal–metal contact, and the surface is mainly damaged by mechanical rolling. After the reconstruction of lubrication film, the next round of electrical erosion begins. The results are helpful for a deeper understanding of the mechanism of bearing erosion in electrical application. [ABSTRACT FROM AUTHOR]

This paper is aimed at the problems of abnormal tribological damage and fluctuation of tribological performance in the self-lubricating composite serving in heavy load spherical plain bearing in aerospace field. The Nomex/PTFE fiber reinforced composite was used to carry out a reciprocating block on ring tribological test, investigating the tribological performance of the material and its wear evolution. Results show that the influence of oscillating frequency on material wear is obviously higher than that of load under high load condition (more than 90 MPa or 180 kN). Under a certain load and frequency condition, friction temperature is a key factor to affect wear behavior of the material. Friction heat plays a dominant role in the process of worn out failure of the material. Too high friction temperature greatly weakens the friction and wear performance, resulting in material failure in a short time. Thermal fatigue is the main tribological damage mode of the material under the high load and high frequency condition, with local worn out occurred. This finding was also verified by SEM analysis of the worn surface and wear debris.

Mo2BC-TiC composites were fabricated by fast hot-pressing sintering method with Mo2BC powder as raw material and nano-TiC powder as sintering additive. The effect of nano-TiC additive (mass fraction of 5%) on microstructure and tribilogical behavior of Mo2BC composite was investigated. The results show that the addition of nano-TiC significantly improves the sintering properties, microstructure and mechanical properties of Mo2BC ceramic. The relative density, Vickers hardness, flexure strength, compressive strength and fracture toughness of Mo2BC composites are 98.9 %, 18.1 GPa, 480.5 MPa, 2.9 GPa and 4.1 MPa ⋅ m1/2, respectively. Transgranular fracture is the main fracture mode of Mo2BC-TiC composite. Mo2BC-TiC composite also exhibites a good tribological properites with the friction coefficient of 0.42 and wear rate of 0.6 x 10-5 mm³/ (N ⋅ m). [ABSTRACT FROM AUTHOR]

Lubricant additive plays an important role in reducing the friction and wear for base oil. MAX phase ceramics may have superior advantages for additive application due to their unique nanolayered structure. In this paper, Ti2SnC ceramic is prepared by sintering the elemental mixtures at 1250 °C. In addition, Cu-coated Ti2SnC ceramic is successfully prepared using a chemical plating method for the first time. It is confirmed that the Ti2SnC ceramic has good self-catalytic activity, and a layer of stacking Cu nano-particles can be deposited on the Ti2SnC surface without pretreatment. When the Cu-coated Ti2SnC ceramic powder is doped into PAO10 base oil, the oil can exhibit excellent lubrication properties, where the friction coefficient is as low as 0.095. A layer of tribo-film can be formed during the sliding process when the Cu-coated Ti2SnC ceramic is incorporated into PAO10 base oil, which can reduce the friction coefficient. The superior lubrication properties can be attributed to the synergistic lubrication effect of Ti2SnC ceramic and Cu nano-particles. [ABSTRACT FROM AUTHOR]

Due to the high speed and high pressure operating conditions, wear between the finger seal and the rotor is inevitable, and this leads to an increase of leakage clearance and becomes an important factor affecting the seal life. The theory of anisotropic elasticity was employed to describe the mechanical characteristics of the seal material. An improved Archard wear model was proposed to calculate the nodal wear rate, and the local wear direction was also determined. The wear simulation model and procedure were established based on the Arbitrary Lagrangian Eulerian adaptive mesh strategy. The effects of material density, fabric orientation, pressure differential and rotor speed on the wear characteristics of finger seal and the change of leakage clearance caused by wear loss were studied. The results show that the wear first occurs at the heel area of the finger foot bottom and gradually extends to the toe area. C/C (carbon fibre reinforced carbon matrix) composite finger seal with higher material density has smaller leakage clearance and wear depth. With the increase of fabric orientation angle, the wear depth in the heel area of finger foot is smaller, and the circumferential wear area is narrower. The average wear depth of finger seal decreases with the orientation angle. When the orientation angle is 0, the seal leakage clearance is smaller. The increase of pressure differential not only aggravates the seal wear, but also expands the wear area, and also increases the average contact pressure and leakage clearance. Increasing the rotor speed make the wear depth of the heel area of finger foot gradually increase, but the wear area becomes narrower. The average contact pressure decreases and the average leakage clearance increases. This study provides a theoretical method and basis for the prediction and evaluation of the wear life and performance of C/C composite finger seal. [ABSTRACT FROM AUTHOR]

CF/PEEK composites were prepared by vacuum hot pressing sintering technology. The thermal properties of the materials were tested by thermal conductivity analyzer and TG tester. Multifunctional friction and wear testing machine, 3D morphology profilometer, scanning electron microscope and friction electrometer were used to analyze the friction and wear properties and anti-friction electrostatic properties of the materials. The results show that with the increase of the forming temperature, the friction coefficient and wear rate of the materials decrease gradually. With the increase of CF contents, the friction coefficient, wear rate and friction electrostatic voltage decrease first and then increase. When the CF content is as 20%, the friction coefficient, wear rate and friction electrostatic voltage reach the lowest values, which are as 0.247, 5.6 x 106 mm/(N ⋅ m) and 3.3 V, respectively. Friction and electrostatic data show that the CF/PEEK materials prepared by this method have better friction properties and anti-electrostatic properties than that of commercial composites. The wear mechanism of CF/PEEK composites is mainly adhesive wear, accompanied by slight abrasive wear. [ABSTRACT FROM AUTHOR]

A novel rotating conductive joint consisting of an inner raceway, an outer raceway, and an elastic ring was proposed in this study. The elastic ring was clamped between the inner and outer raceways using elastic compression force. The effect of the elastic force on the current-carrying properties and the damage of the ring material was investigated. As the elastic force increased from 10.2 N to 20.4 N, the total frictional force decreased from 15.5 N to 9.5 N, and the contact resistance decreased from 0.37 Ω to 0.18 Ω. While monitoring the revolution and rotation of the elastic ring, it was observed that the slip-rolling ratio decreased from 43.04% to 31.74%. Furthermore, a low friction coefficient was obtained under a high elastic force, which could be attributed to the small slip-roll ratio. The scanning electron microscopy and optical microscopy results revealed that a low friction coefficient led to subsurface crack initiation and a low degree of grain deformation. When the friction coefficient at a single contact point was greater than 0.34, fatigue occurred directly on the contact surface. The high friction-induced plastic deformation could cause surface hardening. Therefore, a high friction coefficient and large surface fatigue did not lead to high wear at low elastic forces. [ABSTRACT FROM AUTHOR]