High-resolution characterization of the fretting corrosion of Alloy 690 in the simulated secondary water of pressurized water reactor

•Abrasive wear is the dominant wear mode.•The fretting wear can not only reduce its thickness but also introduce cavities into the oxide grain boundaries.•The fretting wear alters the matrix microstructure underneath the oxide scale, forming a nano-grained layer.•The nano-grained layer accelerates the Cr consumption in the near surface matrix.