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

A tribological comparison was conducted among micro‐MoS2 (m‐MoS2), platelet‐like nano‐MoS2, and spherical nano‐MoS2 in lithium grease, lithium‐calcium grease, and polyurea grease, respectively. Micro‐MoS2 slightly improved the lubrication of the 3 greases. The 2 nano‐MoS2 samples had obvious superiority over m‐MoS2. The tribofilms produced by nano‐MoS2 contained MoS2 and MoO3. However, the tribofilms with m‐MoS2 did not contain Mo, or Mo only existed in the form of MoO3. The absence of MoS2 in tribofilms was the main reason for the poor lubrication of m‐MoS2 greases. Moreover, the improved lubrication of the spherical nano‐MoS2 greases than the platelet‐like nano‐MoS2 ones was ascribed to the lubricating superiority of the spherical structure to the platelet‐like one.