To improve the tribology properties of the polymer coating under elevated temperature, the epoxy coating was reinforced with nano graphene. The micro-hardness, heat conductivity, and thermo-gravimetric properties of the coating were enhanced as filled graphene. The friction and wear properties of the polymer coating were studied using a pin-on-disc tribo-meter under room and elevated temperatures. The results showed that under room temperature, the friction coefficient and the wear rate of the coating adding 4.0 wt % graphene was 80% and 76% lower than that of the neat epoxy coating, respectively. As the test temperature increased, the friction coefficient of the graphene/polymer coatings decreased at first and then slightly increased. The friction coefficient was at its lowest value under 150 °C and then increased as the temperature rose to 200 °C. By adding 4.0 wt % graphene, the friction coefficient and wear rate of the polymer coating were further reduced, especially at elevated temperatures.

In this study, we deposited composite coatings of polyvinylidene fluoride (PVDF) and epoxy resin with La₂O₃ and MoS₂ nanoparticles on the surface of a Babbitt alloy in order to improve its tribological performance. A pin-on-disc tribometer was used to evaluate the tribological properties of the Babbitt alloys with and without the composite coatings. The results showed that compared to the polymer-La2O3 composite coating, polymer-MoS₂ composite coating was more effective in reducing the friction coefficient and the wear rate of Babbitt substrate under both dry and boundary lubrication conditions compared with the polymer-La₂O₃ composite coating. However, the wear rate of the Babbitt alloy with polymer-La₂O₃ composite coating was lower than that of the alloy with polymer-MoS₂ composite coating. The wear scratches were analyzed using a scanning electron microscope (SEM). The worn surface of the polymer-La₂O₃ coating was much smoother and more continuous than that of the polymer-MoS₂ coating, meanwhile transfer films were respectively detected on the pin surfaces. The addition of nanoparticles can reduce the wear rate and friction coefficient of polymer composite coating by forming a transfer film. Hence the polymer composite coating hence can protect the Babbitt substrate.

A grooved texture surface was fabricated to enhance the wear resistance of the guide rail surface of molding machine. The effects of sand concentration in the oil and the groove width on the tribological properties were studied using a pin-on-disk tribometer. Surfaces with groove widths of 1000 μm (S1) and 1500 μm (S2) had lower friction coefficient and better anti-wear properties than a non-grooved textured surface (S0) when lubricated with 0% and 5% sand–oil mixture. However, the friction coefficient and wear rate of S1 and S2 were higher than those of S0 when the sand concentration increased to 10%. The grooved texture surface enhanced wear resistance under low sand concentration because the grooves captured sand particle and prevented them plowing the sliding surfaces. When lubricated with higher sand concentration, the sand could fully fill the grooves, resulting in drastic two-body wear and impact wear. Thus, surface with appropriate grooved texture was favorable for wear resistance.

Finger seals provide favourable flexible dynamic performance and a low level of leakage that is less than that of brush seals and graphite seals. However, the hysteresis caused by the friction between different finger slices or between the finger slice and the back plate strongly affects the working stability. In addition, the wear properties between the finger feet and rotor runway can adversely affect the working stability. Based on the tribological mechanism, wear-resistant coatings can provide a satisfactory solution to these problems. For this purpose, the simulations of finger seal are first performed in ANSYS to verify that good contact surface friction performance can effectively improve the efficiency of finger seal. Then we evaluated the friction performance of WC, Cr₃C₂, and PTFE coatings using a pin-on-disk tribometer. The results showed that the wear-resistant coatings generally exhibited better wear resistance than the substrate material under various load conditions (correspond to the bench test PV of finger seal). The friction coefficient of the 40CrNiMoA substrate was 0.65, while the friction coefficients of WC, Cr₃C₂, and PTFE coatings were 0.22, 0.27, and 0.13, respectively, corresponding to 33.8%, 41.5%, and 20% of the friction coefficient of the 40CrNiMoA substrate. The friction coefficient of the PTFE coating was the lowest due to its self-lubricating property and showed a long service life under low loads; thus, this coating offers a promising solution to reduce the friction-caused hysteresis on a finger seal. Under loads of 20 N and 30 N, the service life of the WC coating was much longer than that of the Cr₃C₂ coating. Even at a load of 50 N, the service life of the WC coating was 4.3 times that of the Cr₃C₂ coating. The wear-resistant WC coating has strong application prospects in improving the service life of finger seals.