Study On High Temperature Fretting Wear Of690Alloy And PCVD Tin/Tisin Multiplayer Films

Fretting was a wear phenomenon occurring when two contact surfaces were subjected to small amplitude(micron degree) relative to oscillatory movement, which could aggravate surface wear and accelerate crack initiations of working components leading to premature catastrophic failures. With the high temperature and strong radiation in the nuclear power industry, the life of the steam generator (SG) tube was decreased due to flow-induced vibration (FIV). Owing to extreme hardness and high temperature oxidation resistance, TiN/TiSiN multiplayer films was used for the research on high temperature anti-wear of SG tube material.The tests had been carried out by using the hydraulic fretting test machine with a high precision, the fretting wear behaviors of the SG tube material (690alloy) and TiN/TiSiN multiplayer films deposited by Plasma Chemical Vapor Deposition (PCVD) on substrate at elevated temperature were studied. The normal load of20-80N, displacement amplitudes of80-200μm was applied at elevated temperature(25,200°C,300°C). The effects of displacement, load and temperature on fretting log, friction coefficient, wear loss, wear morphology and fretting mechanism of690alloy and TiN/TiSiN multiplayer films were analyzed comparatively. The results were drawn as follows:1. The friction coefficient of690alloy and TiN/TiSiN multiplayer films increased as the load increased, but displacement did not have much effect on friction coefficient. The friction coefficient of690alloy at200°C was higher than that at room temperature and300°C, and300°C slightly above that at room temperature. The impact of temperature on friction coefficient of TiN/TiSiN multiplayer films was unremarkable because of its high temperature oxidation resistance. Under the test condition, the friction coefficient of TiN/TiSiN multiplayer films was lower than690alloy, played the role of antifriction.2. When the test temperature was constant, the wear loss of690alloy and TiN/TiSiN multiplayer films increased with the rose of displacement or load. The friction coefficient and wear volume of690alloy at200°C was higher than that at room temperature and300°C, and room temperature was consistent with300°C. Owing to the excellent anti-oxidation abilities, the wear loss of TiN/TiSiN multiplayer films was slightly affected by temperature. Thanks to the extreme hardness and special performance, the wear losses of TiN/TiSiN multiplayer films were lower than690alloys under test conditions, TiN/TiSiN multiplayer films could provide the fretting wear resistance for690alloy.3. The fretting mechanism of690alloy was mainly delamination and abrasion wear at room temperature; while the fretting mechanism was primarily the combination of adhesive at200°C, delamination and oxidative wear; the fretting mechanism was adhesive and oxidative damage at300°C. Owing to the excellent anti-oxidation abilities, the effect of oxidation on TiN/TiSiN multiplayer films was not remarkable. Therefore, the fretting mechanism of TiN/TiSiN multiplayer films was delamination at test temperature, but the damage at300°C slighter than200°C.