Investigation on the Tribological Behaviors of as-sprayed Al2O3 Coatings With the Effects of MoS2 Lubricant and External Loads

The Al2O3-MoS2 ceramic-based lubricating coating was prepared via introducing MoS2 dry film lubricant into the pores and cracks of thermal-sprayed Al2O3 coating by facial paint spraying method. The microstructure, mechanical properties and tribological behaviors of the as-received Al2O3-MoS2 coating were thoroughly evaluated. The results illustrated that MoS2 was mainly concentrated on the shallow surface of the Al2O3 coating, and thus more uniform, more compact and smoother Al2O3-MoS2 coating was obtained. Meanwhile, the mechanical properties of the Al2O3 coating did not change significantly after the introduction of MoS2. The tribological experiments illustrated that compared with the Al2O3 coating, the friction coefficient and specific wear rate of the Al2O3-MoS2 coating under different loads were greatly reduced due to the generation of the lubricating layer. Especially under the load of 5 N, the friction coefficient was as low as 0.36, and the wear rate (1.49×10-5 mm3×(N×m)-1) was almost 17 times lower than that of Al2O3 coating (2.53×10-4 mm3×(N×m)-1). This research established a new and simple way to prepare ceramic-based self-lubricating coatings by using temperature-sensitive solid lubricants.