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This study investigated the fretting wear behavior of the nuclear power material Inconel 690 alloy. An improved PLINT high-temperature fretting tester was used on an Inconel 690 tube against a 1Cr13 cylinder at different temperatures (25 C and 300 C) under alternating load conditions. The fretting-wear mechanism and the kinetic characteristic of Inconel 690 alloy were analyzed. Results showed that the fretting running behavior was closely related to the normal excitation frequency. In parallelogram shaped F t-D curves, the friction fluctuates periodically, and accordingly the fretting was running in the slip regime. The steady-state friction force at room temperature in air was higher than that at 300 C. Moreover, the damage behavior of the fretting for Inconel 690 alloy strongly depended on the normal load, displacement amplitude, temperature, and excitation frequency in atmospheric environment. A superposition effect of fretting wear behavior was discovered because of the combined effect of alternating normal and tangential forces; thus, delamination became more significant. Abrasive wear and delamination were the major mechanisms in Inconel 690 alloy at room temperature in ambient air. The dominant mechanisms at 300 C were the abrasive wear, oxidation wear, and delamination.

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In this study, molecular dynamics simulation was conducted to investigate the frictional behaviors between diamond tool and zirconium (Zr) substrates at the nanoscale. The effects of grain size on friction and wear were discussed under different sliding velocities. The simulation results showed that the friction forces had similar variation tendencies under different sliding velocities. Besides, the friction responses were stronger at high sliding velocities because of the atomic adhesion while the ploughing effect was more obvious at slower sliding velocity. Moreover, both the friction forces and the wear amounts increased with the decrease in the average grain sizes of the substrates. To explain this phenomenon, the internal mechanism was investigated by using the dislocation extract algorithm and the atomic displacement analyses. The results showed that the [0001]-oriented single crystalline substrate was prone to form continuous dislocation structures moving tangentially along the sliding direction due to the characteristic of Zr's slip systems, whereas grain boundaries conducted the deformation further into the polycrystalline substrates, increasing the contact areas and causing atomic accumulation in front, both resulted in stronger friction responses and wear. Accordingly, with the decrease in average grain sizes, the substrates experienced more severe subsurface damage and the deformation mechanism of nanocrystalline Zr had evolved from dislocation emission to grain boundary rotation and sliding.