Investigation of the tribological properties of polyfluo wax/polyurethane composite coating filled with nano-SiC or nano-ZrO2

Effect of nano-SiC or nano-ZrO2 on the friction and wear behaviors of the polyfluo wax (PFW)/polyurethane (PU) composite coating was studied using a ring-on-block wear tester under dry friction condition, and the worn surfaces of the PFW/PU composite coating and the transfer films formed on the surface of the counterpart ring were investigated by SEM and optical microscope, respectively. The structural changes of the PFW/PU coating filled with nano-ZrO2 during the friction process were investigated with a Fourier transform infrared microscope. It was found that nano-SiC or nano-ZrO2 as the fillers contributed to improve the friction-reducing and anti-wear abilities of the PFW/PU coating. Especially, the anti-wear ability of the filled coating is the most effective when content of nano-ZrO2 is 5.0 wt.%. Furthermore, we studied the effect of curing temperature, sliding speed and applied load on the friction and wear behaviors of the PFW/PU coating filled with 5.0 wt.% nano-SiC or 5.0 wt.% nano-ZrO2. The results showed that the friction and wear behaviors of all coatings were much better in lower curing temperature than those in higher curing temperature. The friction coefficient of the composite coatings reinforced with different fillers decreased with increasing sliding speed and applied load, and the anti-wear behavior of the coating filled with 5.0 wt.% ZrO2 was the best under 420 N and at a speed of 2.56 m/s. The investigations of the frictional surfaces showed that the fillers of nano-SiC or nano-ZrO2 were able to enhance the adhesion of the transfer films of the PFW/PU coating to the surface of counterpart ring, so they significantly reduced the wear of the PFW/PU coating. FTIR analyses indicated that the occurrence of the tribochemical changes during friction process mainly involved disordering and partial decomposition of the polyurethane binder.