Lubrication and Failure Mechanisms of Molybdenum Disulfide Films

The friction, wear, and wear life of rubbed molybdenum disulfide (MoS2) films were studied in a pin-on-disk sliding friction and wear apparatus. The films were applied to 440C HT (high temperature modified) stainless-steel disks with three surface finishes - polished (0.094.02 pm CLA), sanded (0.304.05 pm CLA), and sandblasted (1.24.2 pm CLA). The films were evaluated in moist air (10 000-ppm H20) and dry argon. Optical microscopy was used to study the lubricating films, the transfer films, and the wear process. Observations were made at preset intervals throughout the wear lives of the films by stopping the tests and removing the specimens from the apparatus. During the "run-in, " very smooth, flat plateaus were created on the rider and metallic asperities (on the rough substrate surfaces) in the MoS2 film wear track. The lubrication mechanism was the flow of thin films of M0S2 between the flat plateaus on the two opposing surfaces. The valleys on the roughened substrate surfaces served three purposes: They restricted the transverse flow of the MoS2 out of the contact area during the run-in, they acted as reservoirs for supplying MoS2 to the contact area, and they acted as deposit sites for wear debris. Thus, in general, wear life was extended by increasing the surface roughness of the substrate; however, the friction coefficient was not markedly affected. The chemical transformation occurred rapidly in moist air; thus, wear life was about two orders of magnitude greater in dry argon than in moist air. Increasing the substrate roughness also extended wear Life (in both atmospheres), but the effect was not as great as the atmosphere effect (less than one order of magnitude). The friction coefficient was not affected by substrate roughness in dry argon; however, rougher substrates gave lower friction coefficients in moist air than smoother substrates. Rider wear rates during run-ins were higher on rougher substrates for both atmospheres. After run-in in dry argon, substrate roughness did not greatly affect rider wear rate; however, after run-in in moist air, the rougher the substrate, the lower the rider wear rates. If you are looking for high quality, high purity, and cost-effective Molybdenum disulfide or the latest price, please email contact mis-asia.

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