Effect of normal force on the fretting wear behavior of Inconel 690 TT against 304 stainless steel in simulated secondary water of pressurized water reactor

For understanding the long term fretting mechanism, the effect of normal force on the fretting wear behavior of 690 TT heat transfer tube against 304 stainless steel (SS) ball in simulated secondary water with 106 total fretting cycles was studied. The changes of the friction coefficients can be divided into five stages: small and slowly increase stage, sharply increase to a peak point, dramatically decrease to a steady value, steady stage, and continuously increase stage. And the friction coefficient decreases with the increase of the normal force. The morphologies of the worn scars under different normal forces are quite different. A stratified layer structure is formed on the 690 TT surface during the fretting wear process when the normal force is 60N.