Comparison of Grease and Solid Lubrication of Rolling Bearings Under Small-Stroke Reciprocation for Space Applications

Abstract

Rotary actuator is a device responsible for the precise rotation of sensitive instruments such as antennas. Requirements for its precision and stiffness are extremely high. Actuators used in the space environment have to work for long period, under extreme condition and without possibility of repair or replacement. One of the main components responsible for its proper function are bearings. They precisely support shafts, and usually operate in a very small angular range with many repetitions. Selection of the proper bearing design and also the lubrication of the bearing can have significant effect on the performance and life of the entire satellite. Purpose of this study was to select and test suitable lubricant to support operation of such bearing. Sets of bearings lubricated by Rheolube 2000 and MoS2 PVD film were tested in thermal vacuum chamber under small angle oscillatory motion with the same start and end position for every cycle. Torque and bearing noise was evaluated during the tests and bearings were inspected. Rheolube 2000 was selected as the best lubricant for the described conditions because of the acceptable torque, lower bearing noise and easier manipulation during assembly and testing. However, both options proved to be applicable.

Layered 2D Nanomaterials to Tailor Friction and Wear in Machine Elements—A Review

“…Numerous studies have assessed the ability of 2D materials to improve friction, wear, and service life in rolling element bearings, [137] such as axial [29,[138][139][140] and/or radial bearings [141][142][143][144][145][146] as well as with [29,[141][142][143][144][145][146] and without retainer elements or cages. [138][139][140]147] The availability of fully developed industrial-scale PVD processes for deposition of the MoS 2 coatings resulted in MoS 2 being the most studied material among others.…”

“…[138][139][140]147] The availability of fully developed industrial-scale PVD processes for deposition of the MoS 2 coatings resulted in MoS 2 being the most studied material among others. [138][139][140][141][142][143][144][145] Yet, some application-oriented studies on WS 2 , [148] graphene, [146] and MXenes [29] have been performed as well. Apart from coatings for the highly loaded primary contacts between rolling elements and the raceways of bearing rings/washers, [29,[138][139][140][141][142][143]146] some studies addressed secondary contacts with lower loads but higher slip and sliding velocities such as the contact between the rolling elements and cage pockets with 2D nanomaterials as inserts or reinforcement phases of composites.…”

“…[138][139][140][141][142][143][144][145] Yet, some application-oriented studies on WS 2 , [148] graphene, [146] and MXenes [29] have been performed as well. Apart from coatings for the highly loaded primary contacts between rolling elements and the raceways of bearing rings/washers, [29,[138][139][140][141][142][143]146] some studies addressed secondary contacts with lower loads but higher slip and sliding velocities such as the contact between the rolling elements and cage pockets with 2D nanomaterials as inserts or reinforcement phases of composites. [141,144,145,147,149] Depending on the targeted application, the evaluated testing conditions ranged from atmospheric [29,[138][139][140]146,147] to vacuum [140][141][142][143][144]149] and nitrogen environments.…”

“…Apart from coatings for the highly loaded primary contacts between rolling elements and the raceways of bearing rings/washers, [29,[138][139][140][141][142][143]146] some studies addressed secondary contacts with lower loads but higher slip and sliding velocities such as the contact between the rolling elements and cage pockets with 2D nanomaterials as inserts or reinforcement phases of composites. [141,144,145,147,149] Depending on the targeted application, the evaluated testing conditions ranged from atmospheric [29,[138][139][140]146,147] to vacuum [140][141][142][143][144]149] and nitrogen environments. [138] Initial studies on using TMDs, primarily MoS 2 , for the solid lubrication of rolling bearings were mainly driven by the need for tribologically efficient coatings for space exploration and aeronautics applications.…”

“…Recently, David et al [143] compared 1 µm thick MoS 2 solid lubricant coatings on the rollers and raceways with vacuum grease boundary/mixed lubrication of angular contact ball bearings in a space application test-rig. For MoS 2 -coated bearings, the original cage was replaced with a PTFE/MoS 2 fiberglass composite.…”