THE SYNERGISTIC EFFECTS OF MO AS AN ALLOY ELEMENT ADDED TO CHROMIUM CARBIDE COATINGS ON THEIR LUBRICATION PROPERTIES AT HIGH-TEMPERATURES

This paper studies the effects of Mo, added to a plasma-sprayed Cr3C2- 25%NiCr coating, on the anti-friction performance of the coating at te mperatures up to 850-degrees-C. 7% Mo is mixed with Cr3C2-25%NiCr powd er for spraying the Cr3C2-NiCr-Mo coating. The surface of this kind of coating is found to react with additive elements in synthetic oil in the friction process when sliding against a plasma-sprayed Cr2O3 coati ng at high temperatures. The reacted surface film shows the effect of solid lubrication. Compared with the Cr3C2-NiCr coating, the Cr3C2-NiC r-Mo coating possesses much better anti-friction capability at high te mperatures. Surface analysis using SEM, WDS and XPS shows that Mo play s a very important role in forming different kinds of solid lubricatin g films at different temperatures. The solid lubricating films formed are dominated by MoS2 and graphite.