Tribological properties of 3 types of MoS₂ additives in different base greases

A tribological comparison was conducted among micro‐MoS 2 (m‐MoS 2 ), platelet‐like nano‐MoS 2 , and spherical nano‐MoS 2 in lithium grease, lithium‐calcium grease, and polyurea grease, respectively. Micro‐MoS 2 slightly improved the lubrication of the 3 greases. The 2 nano‐MoS 2 samples had obvious superiority over m‐MoS 2 . The tribofilms produced by nano‐MoS 2 contained MoS 2 and MoO 3 . However, the tribofilms with m‐MoS 2 did not contain Mo, or Mo only existed in the form of MoO 3 . The absence of MoS 2 in tribofilms was the main reason for the poor lubrication of m‐MoS 2 greases. Moreover, the improved lubrication of the spherical nano‐MoS 2 greases than the platelet‐like nano‐MoS 2 ones was ascribed to the lubricating superiority of the spherical structure to the platelet‐like one.