In sodium-cooled fast reactors,the flow-induced vibration between the coolant and components in the heat exchanger can cause fretting wear of the heat transfer tubes.2.25Cr1Mo steel,a candidate material for the heat transfer tube of the fourth-generation sodium-cooled fast reactor,was taken as the research object.The tangential fretting wear behavior and damage evolution of 2.25Cr1Mo steel under different normal loads (10 N,20 N,30 N) were studied.Optical microscope (OM),scanning electron microscope (SEM) and EDS were used to analyze the tribo-chemical reaction of the wear scar and the composition of local micro-area,and the wear volume of the 2.25Cr1Mo steel was obtained by a white light interferometer.The results show that with the increase of normal load,the fretting mode of 2.25Cr1Mo steel changes from full slip to partial slip.The friction coefficient and the wear volume first increase and then decrease with the increase of the normal load.When the load is from 10 N to 20 N,the main wear mechanisms of 2.25Cr1Mo steel are abrasive wear,delamination and oxidative wear,when the load is 30 N,the main wear mechanisms are adhesive wear,plastic deformation and oxidative wear.