Adhesive Wear and Exploratory Testing of Aerospace Bearing Steels

Abstract

Scuffing is a failure mode of contacting surfaces in relative motion that results in deformed topographies, loss of lubricant film, spallation, and potential seizure of machinery. A recent test campaign utilized a ball-on-disk tribometer to evaluate various types of bearing steels for their resistance to adhesive wear, which is a precursor to more severe scuffing. In these tests, the load, temperature, and slide-to-roll ratio (slip) were kept constant, while the entraining velocity was incrementally decreased. If no scuffing occurred, additional tests of higher slip were then performed. A scoring criterion was employed to give each material combination a numerical score, with a higher score indicating better resistance to adhesive wear. Under this approach, most combinations received the maximum possible rating. While this result indicated the robustness of these steels against this failure mode, this test approach would leave the impression that the varying characteristics of these steels are not active in a material's scuffing response. Therefore, following this initial test campaign, an alternative test procedure was explored to obtain improved material discrimination. For this approach, the entraining velocity was held constant while the amount of sliding in the contact was incrementally increased by increasing the slide-to-roll ratio. Preliminary trials with this second procedure indicated improved material discrimination for resistance to adhesive wear and scuffing and showed additional benefits of reduced run time and greater simplicity in the test procedure.