Deposition, characterization, and performance of tribological coatings on spherical rolling elements

Abstract

Abstract Increasing demands on the performance of intricate parts like bearings in biomedical and aerospace systems have created the necessity for tribological coatings that can enable systems to achieve enhanced performance in challenging environments. In this work, we have developed a process to deposit wear-resistant (Cr x N, WC/a-C:H, TiC/a-C) and solid lubricant (Ti–MoS 2 ) coatings onto spherical rolling elements. The tribological performance of coated specimens has been evaluated under boundary layer lubrication in rolling and sliding contact tribometers. Although all of the coatings are wear-resistant under sliding contact, only Ti–MoS 2 coated balls provide a significant improvement over uncoated balls in rolling contact fatigue experiments. Specifically, in rolling contact fatigue experiments performed using M50 steel rods, Ti–MoS 2 coated balls improved L 50 life by more than two times over uncoated balls. Ti–MoS 2 appears to be a promising candidate for rolling bearing applications in both lubricated and unlubricated conditions.