Progresses on cryo-tribology: lubrication mechanisms, detection methods and applications

Abstract

Tribology at cryogenic temperatures has attracted people’s attention since the 1950s with the acceleration of its applications on hi-tech equipment such as the cryogenic wind tunnel, liquid fuel rocket, space infrared telescope, superconducting device, planetary exploration, which requires solid lubrication for moving parts at low temperature down to 4 K in cryogenic liquid, gaseous or vacuum environments. Here the research progresses on cryo-tribology are reviewed. Tribological properties and mechanisms of solid lubricants listed as carbon material, molybdenum disulfide (MoS2), polymer and polymer-based composite, etc. with decreasing temperature are summarized. The friction coefficient was found to increase with decreasing temperature induced by thermally activated processes. The mechanism of transfer film formation should be noticed as a significant way to promote the tribological properties of the solid lubricant. On the other hand, applications of solid lubrication on moving parts under cryogenic conditions such as the spherical plain bearing, roller bearing are introduced. Tribological test technology of materials and bearings at cryogenic temperatures is summarized where the environmental control, motion and loading realization, as well as friction and wear measurement together at low-temperature environment result in the difficulties and challenges of the low-temperature tribotester. It is worth mentioning that novel technologies and tribotesters were developed for tribo-tests and tribological studies of solid lubricant, spherical plain bearing and roller bearing respectively by overcoming the limitation on cooling in vacuum, resolution of friction measurement, etc., and concentrating on in-situ observation of friction interface aiming to not only promote a deep understanding of friction and wear mechanism at low temperatures, but also give insights into performance of moving parts or components in cryogenic applications.

Review of Wind Power Bearing Wear Analysis and Intelligent Lubrication Method Research

“…The main factors affecting bearing wear are bearing materials, lubricant selection, and environmental factors [33]. Therefore, it becomes crucial to analyze the wear of wind power bearings to reduce the repair and maintenance costs of wind power bearings [25,34]. The following are the roles of each of the wind turbine bearings and the main forms of wear.…”

“…However, over time, the continuous workload causes wear and tear on the bearings [71]. Lubricants are essential for maintaining the long-term, optimal performance of bearings [34,75]. Compared with other industries, the lubricants used in wind power bearings have higher performance requirements [76].…”

“…Gearbox bearings are the most susceptible to failure, followed by main shafts and pitch bearings [86]. Lubrication is one of the effective ways to reduce bearing failure, it can not only reduce bearing friction and wear but also avoid damage to other parts, reducing the failure rate of wind turbines which plays an important role [34,87,88]. According to the statistics, the bearing failure rate due to lubrication failure is up to 70%, and the causes can include unqualified lubricant quality, premature lubricant failure, lack of lubricant, over-lubrication, and incorrect lubricant selection [35,89,90].…”

Failure Mechanism of Bearings under Extremely Cryogenic Conditions

“…No matter for new energy mining equipment (such as cryogenic pumps) or aerospace equipment (steering gear, rocker arm, etc. ), bearing, as one of the most critical parts of rotating equipment, has gradually attracted the attention of more and more researchers in the field of cryogenic research [1][2][3][4][5][6].…”

GNBoost-Based Ensemble Machine Learning for Predicting Tribological Properties of Liquid-Crystal Lubricants

“…Tribology plays a critical role in both industrial production and everyday life, with extensive applications in aerospace, transportation, bridge engineering, and geological exploration. 1 It is estimated that 30% of the world's annual energy is lost due to friction, and the inclusion of lubricants is an effective means of reducing the coefficient of friction (COF). 2 This method can help to lower the energy consumption and mitigate environmental impacts, providing both economic and environmental benefits.…”