The wear behavior of Ti6Al4V blade rubbed against nickel–graphite (Ni–G) abradable seal coating was studied with a high-speed rub test rig. According to the test results acquired at different incursion per passes and linear speeds, blade wear increased with the increment of linear speed at a fixed incursion per pass. With incursion per pass increasing, blade wear increased when linear speed was fixed at 30 m/s, while decreased at 90 and 150 m/s. Referring to the macromorphology observation, scanning electron microscopy (SEM) and dispersive X-ray spectroscopy analyses of the wear scars, rubbing at 30 m/s, microcutting and microploughing with coating adhesion was the main blade wear mechanism while spalling accompanied by densification was the main coating wear mechanism. Rubbing at 90 and 150 m/s, plastic deformation was the main blade wear mechanism while transfer mixed layer that resulted from blade transferred was identified as the main coating wear mechanism. Quantitative analysis of coating densification and microhardness detection of the transfer mixed layer indicated that high coating densification made great contribution to low blade wear at 30 m/s and aggravated blade wear at high linear speed was due to the high frictional heat and the resultant high-hardness transfer mixed layer. It could therefore be concluded that high linear speed guarantees enough frictional heat output while low incursion per pass is responsible for the accumulation of frictional heat.

The tribological behavior of zinc phosphate impregnated graphite (ZPIG) against nickel-based superalloy (GH4169) in oil environment was investigated, and the lubrication and wear mechanism were also determined in this study. Tribological tests were run under different tribological conditions using a ring-on-disk device. The results showed that, under any load conditions, zinc phosphate impregnated graphite had the lowest coefficient of friction (COF) and wear-rate at 200 rpm. Under the identical rotating speed condition, the minimum coefficient of friction and wear-rate were obtained when the load was 500 N and 1000 N. The lubrication mechanism, which could be reflected by the transfer layer of friction counterpart, was related to the coefficient of friction, wear-rate, and oil temperature to affect contact characteristics of two solid surfaces and formation ability of liquid film. The wear mechanism of zinc phosphate impregnated graphite under oil lubrication conditions was dominated by abrasive wear and material removal was achieved through the fracture mechanism.

Several criteria for fretting wear behavior evaluation have been established since the proposal and establishment of the fretting loop concept. In this article, system deformation and system deformation ratio were defined. In addition, the fretting running conditions were distinguished from the evolution of system deformation with fretting cycles during fretting wear tests under different applied displacements and loads. In the gross slip regime, the system deformation was independent of the applied displacement and increased as the load increased, whereas in the partial slip regime, the system deformation was independent of the load and increased with the applied displacement. Furthermore, a linear relationship between the system deformation and the applied load in gross slip regime was found for the first time. Based on this linear relationship, the system deformation ratio can forecast the running regime with a given load and displacement. For the titanium alloy fretting pairs studied in this article, the fretting wear was found to run in the gross slip regime if the system deformation ratio was smaller than 0.9. Based on these observations, the system deformation ratio exhibited applicability in assisting the mechanical design of equipment suffering from fretting wear.