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Epoxy with ultra-high molecular weight polyethylene (UHMWPE) and MoS2 fillers was coated on a bearing steel (SAE 52100). Frictional and wear properties of the coated samples in sliding contact were investigated on a pin-on-disc tribometer under a normal load of 10 N and a linear sliding speed of 1 m/s against a bearing steel ball. The optimized coating composition (72 wt% Epoxy + 7 wt% hardener + 18 wt% UHMWPE + 3 wt% MoS2) showed highly improved tribological properties compared to pure epoxy and other epoxy-based composites. There was 75% reduction in the coefficient of friction (COF) in the dry interfacial condition (COF reduced from 0.2 to 0.05) over pure epoxy and 80% reduction with grease as the lubricant. The specific wear-rate of the composite was lower by five orders of magnitude over that of pure epoxy. Other mechanical properties such as hardness, tensile strength, and Young's modulus of the composite showed increments of 86%, 121%, and 43%, respectively, with respect to those of pure epoxy. 2–3 wt% of MoS2 had drastic effects on improving strength and reducing friction and wear of the composites. For dry sliding, initial abrasive and adhesive wear mechanisms led to transfer film formation on the steel counterface, and the shearing was mainly within the transfer film. For the grease-lubricated case, a thin layer of grease helped in easy shearing, and the transfer film formation was avoided. This epoxy-based composite will have applications as tribological coatings for journal bearings.

Liquid absorption and tribological studies of epoxy-based composite with ultra-high molecular weight polyethylene and MoS2, sliding against steel, were conducted. Composites, as coating and as a bulk, were soaked in water, base oil, ionic liquid, and lithium-based grease for different intervals of days or months. Liquid weight percent gain was more in polar liquids when compared to non-polar. Coated composite soaked in grease for 10 days showed coefficient of friction of 0.08 with wear life of more than 1 million cycles and wear-rate of 1.7 × 10−8 mm3/N m. Bulk polymer composite soaked in grease for 180 days provided the least coefficient of friction of 0.06 and specific wear-rate of 2.60 × 10−7 mm3/N m.

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