Impact fretting wear of alloy 690 tubes at 25 °C and 290 °C

Flow-induced vibration causes impact fretting wear on the steam generator tubes against their support plates in nuclear power plants. In this paper, to examine the effects of temperature, the impacting load and work rate on the wear, the impact fretting wear tests were performed in room temperature and 290 °C water, simulating the relative movement of the steam generator tube material (Alloy 690) against the tube support plate material (409 stainless steel). The worn surface was observed by SEM, and the wear coefficients of Alloy 690 were evaluated on the basis of the work-rate model. The results showed that wear coefficients of the impact fretting wear at 290 °C were larger than those at room temperature. The wear rate in the 290 °C range was 10 times greater than that in the room temperature range. The SEM observation of worn surfaces suggested that, at room temperature, the wear mechanisms of the impact fretting wear were abrasion and plastic deformation, while at 290 °C, they were adhesion and plastic deformation. In the small fretting amplitude tests, below 300 μm displacement, it was found that the impact force was more damaging than the fretting amplitude.