Damage mechanism of Alloy 690TT mated with Type 304 stainless steel during fretting wear in partial slip regime

Damage mechanism of Alloy 690TT mated with Type 304 stainless steel (SS) subjected to fretting wear in partial slip regime was investigated. The results indicated that material transfer occurred in stick region and micro-slip region of the worn surfaces. The formation of tribologically transformed structure (TTS) was attributed to the dynamic recovery of deformed structures with high density of dislocations. The TTS layer was characterized by roughly equiaxed grains with an average size of ~ 282 nm. The oxidation behavior only occurred in micro-slip region, which resulted in the formation of the ultrafine-grained third body layer (TBL) containing the oxides of Ni(Cr,Fe)2O4 and Cr2O3. The TBL was characterized as having a multilayered structure. The external part was mainly composed of Fe-rich oxides because of the Fe-rich material transferred from 304SS and its subsequent oxidation. The inner one contained Ni-rich oxides which was derived from the oxidized substrate of Alloy 690TT.