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The development of a high-performance solid-lubricating composite with excellent self-lubricity over a broad temperature range in vacuum is significant to solve the frictional problems of spatial mechanisms. In this study, the vacuum tribological behaviors of nickel-matrix/Ag/(Ca, Ba)F2/graphite (0–2 wt%) composites were studied from 25 to 800 °C. The results show that the synergistic effects of solid lubricants can significantly improve the tribological properties of the composites in vacuum, with the graphite content contributing considerably. For 2 wt% graphite, a low friction coefficient (0.14–0.25) and the lowest wear rate ((0.12−4.78)×10−5 mm3·N−1·m−1) were observed in vacuum over the entire testing temperature range. Moreover, the wear mechanisms were clarified via analysis of the chemical composition and morphologies of the sliding surfaces. [ABSTRACT FROM AUTHOR]

It is a challenge to design self-lubricating materials that exhibit and maintain reduced friction coefficient as well as high strength over a wide range of temperatures. A high-temperature self-lubricating nickel-alloy-based composite was created using the hot pressing technique. The composite exhibited high relative density, and simultaneously superior lubricating properties, average friction coefficient below 0.25 from room temperature to 800 °C, and high strength, 470 MPa of tensile strength and 1500 MPa of compressive strength. The composite was very promising in high-temperature tribology. [ABSTRACT FROM AUTHOR]

Abstract: The tribological properties of Ni-17.5Si-29.3Cr alloy against Si3N4 were studied on a ball-on-disc tribotester between room temperature and 1000°C. The effects of temperature on the tribological properties of the alloy were investigated. The worn surfaces of the alloy were examined using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results indicated that the tribological behavior of the alloy expressed some differences with increase in testing temperature. At low and moderate temperatures (below 800°C), the alloy showed excellent wear and oxidation resistances, and the wear rate of the alloy remained in the magnitude of 10−5 mm3/Nm; but at elevated temperature (800–1000°C), the wear and oxidation resistances decreased, and the wear rate of the alloy increased up to 10−4 mm3/Nm. The friction coefficient decreased from 0.58 to 0.46 with the rising of testing temperature from 20 to 600°C, and then remained nearly constant. The wear mechanism of the alloy was mainly fracture and delamination at low and moderate temperatures, and transformed to adhesive and oxidation at elevated temperatures. [Copyright &y& Elsevier]

In aerospace, some moving parts will meet with simultaneous high temperature and vacuum environments. In this study, the tribological behavior of a nickel alloy matrix solid lubricant composite was contrastively investigated under both air and vacuum conditions from room temperature to 800 °C. Results showed that both the friction coefficient and the wear rate of the composite were highly dependent on testing temperature and atmosphere. The friction coefficient in vacuum was lower than that in ambient air. The compositions of the frictional surfaces were analyzed, based on which, the mechanism of friction and wear was proposed. [ABSTRACT FROM AUTHOR]

High-temperature self-lubricating nickel-alloy based composites with Ag and three amounts of BaF2/CaF2 eutectic were prepared by hot press sintering technique. Both the composites with 5wt% and 10wt% BaF2/CaF2 eutectic exhibited markedly higher strength than 15wt% composite. The friction coefficient of the three composites was comparable. All three composites showed the highest wear rate at 600°C, but very lower at 800 and 900°C. The friction coefficient of the three composites was slightly lower as sliding against Si3N4 than Inconel 718. The friction and wear mechanism was proposed. [ABSTRACT FROM AUTHOR]