Revealing the Tribological Mechanism of Synergistic Effect between MoDTC and P-containing Additives in Aluminum-based Grease

Organic molybdenum is of great importance in the application of both liquid and solid lubrication due to its outstanding comprehensive tribological properties. In this work, we prepared a molybdenum dialkyldithiocarbamate (MoDTC) with excellent friction-reducing and antiwear properties in aluminum-based grease by decreasing COF and WSD up to ~ 40.6% and ~ 34.8%, respectively. Furthermore, the tribological properties are further enhanced by combining with traditional zinc dialkyldithiophosphate (ZDDP), indicating excellent synergistic effects on both friction-reducing and antiwear, in which the COF and WSD of aluminum-base grease are reduced by ~ 58.1% and ~ 49.3%, respectively, due to the generation of composite tribofilm composed of MoS 2 , MoO 3 , molybdate and sulfide during the friction process. Moreover, we demonstrated that the P element plays a facilitating role in the tribochemical reaction to transform molybdenum into MoS 2 , which is the critical component of the tribofilm for excellent friction-reducing and antiwear properties.