Frequency induced fretting corrosion mechanism evolution of Alloy 690 exposed to simulated secondary water

Abstract

The effect of frequency (5–30 Hz) on the fretting corrosion behavior of Alloy 690 tube was investigated in simulated pressurized water reactor secondary water. The results show that the wear volume of the tube increases by ∼19 times with the frequency increases, and the wear mechanism changes from adhesive wear to delamination wear and abrasive wear. The increasing fretting frequency could affect the contact temperature and accelerates the change of contact stress, which cause a shift in the wear mechanism. Under the synergic effect of mechanical wear and corrosion, a gradient multi-layer structure is formed on the wear area, which is composed of the ultra-fine grain three-body layer, the tribologically transformed structure layer and matrix distributed from top to bottom. The three-body layer is mainly composed of Fe-rich spinel oxides and a small amount of Fe3O4 and Cr2O3, and its thickness increases with the increase of the fretting frequency.