Effect of MoS2 Nanoflakes on Mechanical and Tribological Behavior of Composite Friction Material Fabricated by Pressure-Assisted Sintering

The MoS2 nanoflakes can be a novel candidate as a solid lubricant in fabricating friction material for automotive brake-pad disc systems. In this paper, an investigation has been made to analyze the effect of MoS2 nanoflakes on the mechanical and tribological behavior of the formulated copper-free low-metallic composite friction material. Three samples, namely S-1, S-2 , and S-3, have been fabricated containing different types of solid lubricant. Sample S1 had a solid lubricant as graphite, while samples S-2 and S-3 had graphite mixed with solid lubricant MoS2 with average flake sizes of 2 mu m and 50 nm, respectively. Other components included steel, PAN, and aramid as reinforcing fibers; walnut powder, barium sulphate (BaSO4), and nitrile-butadiene rubber as fillers; phenolic resin as a binder; and FeO, Quartz, and MgO as abrasives. A pin-on-disc tribometer test (ASTM G-99) was conducted to carry out the wear test at a load of 60 N, sliding velocity of 2.09 m/s, and sliding distance of 6283 m at room temperature. A scanning electron microscope was used to study the micro-structural evolution of worn composite friction pin material. The results show that the nano-sized MoS2 solid lubricant influences the structural integrity of the formulated composites, which governs the friction and wear behavior. The graphite and MoS2 -based friction composites S-2 and S-3 perform better than the conventional friction material (S-1) containing graphite in terms of physical-mechanical, thermal, and tribological properties. The specific wear rate of the S-1 sample is the highest (2.72 x 10(-5 )mm(3)/Nm) followed by S2 (1.84 x 10(-5) mm(3)/Nm) and S-3 (0.98 x 10(-5) mm(3)/Nm) respectively. The graphite and MoS2-based friction specimens S-2 and S-3 showed adequate coverage of friction plateaus, reducing wear and abrasion of the counter disc.