Metallurgical analysis of surface distress on balls during the operation of AISI 440C ball bearings for satellite applications

Abstract

Bearing damages in reaction/momentum wheels are detrimental to the life and performance of the spacecraft. The signature of performance degradation in spacecraft ball bearings includes an increase in the bearing friction as evidenced by the increase in wheel current with a simultaneous increase in the wheel bearing temperature. The potential source of the problem should be addressed to avoid the irreversible impact on mission life. This paper presents the details of metallurgical analysis conducted on AISI 440C ball bearings to address the issues which perhaps contribute to the above problem and suggest possible remedial measures to avoid the recurrence of such issues. During ground testing, surface distress/running tracks were noticed on the contact surfaces of the balls. Detailed metallurgical analysis revealed loss of hard/coarse primary carbides from the matrix. In a closed system, these particles once removed, can contaminate the lubricant and cause further surface distress and progressive damage to the contact surface.