Effect of wear-resistant coatings on the comprehensive performance of finger seal

Abstract

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.