Influence of the moist air humidity (10-70%) on the fretting characteristics of steels under grease lubrication is experimentally investigated. Ball (bearing steel. JIS SUJ2) on disk (carbon steel. JIS S15C) type fretting tests for 0-20 mg of grease supplied before each test at the punctual contact between ball and disk were conducted at 50 μm slip amplitude and 6. https://www.roneverhart.com/Western-Digital-Ultrastar-DC-HC550-WUH721816ALE6L0-0F38460-16TB-7-2K-RPM-SATA-6Gb-s-512e-ISE-3-5in-Hard-Drive/