High Temperature Tribological Properties of Modified CF in MoS₂ Composite Coating

After the CF was acidified, the fiber surface was silanized with KH550, and the carbon fiber powder after the GO and silanized treatment was poured into DMF solution. Finally, the GO was chemically grafted on the CF surface, which was denoted as CF-GO. CF-GO was added into MoS₂ coating according to the mass fraction of 0.0%, 0.5%, 1.0%, 1.5% and 2.0%, respectively, to prepare coatings of different proportions. With the help of CFT-Ⅰ high-speed reciprocating friction and wear testing machine, and other conditions unchanged, the friction and wear experiments were carried out on five kinds of coatings under different addition ratios at the matrix temperatures of 20, 50, 100 and 200 ℃, respectively. Meanwhile, the surface wear morphology data of the coatings under different conditions were observed by the ultra-depth of field microscopic system. The wear mechanism of the coating was further analyzed by SEM, and the influence of temperature and the proportion of modified powder on the wear resistance and heat resistance of the coating was explored. The experimental results showed that: after infrared analysis of modified powder CF-GO, it was found that a secondary amide N-H characteristic peak appeared at 3 243 cm⁻¹ on its surface, which was the amidation reaction between the amino group on the surface of carbon fiber after silanization and the carboxy group on the surface of GO to form an amide bond. The characteristic peak of C=C appeared at 1 628 cm⁻¹ and the characteristic peak of Si-O-C appeared at 1 125 cm⁻¹. XPS analysis showed that CF had different types and contents of elements at different stages, because different chemical treatments would change the types and contents of elements on CF surface. Finally, scanning electron microscopy was used to observe the morphology of CF before and after modification, and it was found that compared with the original CF, sheets of GO appeared on the surface of the modified CF. All these indicated that GO had been chemically grafted on carbon fiber. After testing the binding strength of the coating at room temperature, it was found that the maximum binding strength was 14.1 MPa when 1.5% CF-GO was added. At the experimental temperatures of 20, 50 and 100 ℃, the wear resistance of the coatings prepared by adding 1.5% CF-GO coating was better than that of other coatings. Compared with the coatings without modified powder, the wear depth of the coatings decreased by 33.3%, 23.6% and 14.2%, respectively. When the substrate temperature was 200 ℃, the wear depth of the coating with 1.5% CF-GO was reduced by 66.1% compared with the unmodified coating, and the wear resistance of the coating was improved to a great extent. This is because the modified carbon fiber can export heat inside the coating to the surface, and the graphene oxide on the surface can better combine the resin with the fiber. By giving full play to its optimization effect on high temperature deformation resistance, wear resistance and other properties, analysis of the wear topography of the coating surface showed that the height of the deformation zone of the coating was only 9.24 μm, the micro-cracks at the bottom of the wear mark were the least, and the area of the massive falling pit at the bottom was smaller than that of other proportions of the coating. Further analysis of the cross section morphology of the coating showed that, when 1.5% CF-GO was added, the fibers inside the coating form a network skeleton structure, which could maximize the enhancement effect of CF-GO. This study proved that coatings with 1.5% CF-GO had better heat resistance, stability and wear resistance, indicating that nano-carbon fibers modified by GO had good potential to effectively enhance the comprehensive properties of resin coatings.