Investigation into the fretting corrosion of alloy 690 TT against type 304 stainless steel in high temperature pure water under partial slip conditions

Fretting corrosion of Alloy 690 TT against Type 304 stainless steel (SS) can occur in the steam generators of a nuclear power plant under partial slip conditions. In this study, galvanic corrosion occurred before fretting, leading to faster corrosion of 304SS with larger polyhedral and flaky spinel oxides and slower corrosion of Alloy 690 TT with smaller polyhedral spinel oxides, which resulted in polygonal and flaky micropitting of Alloy 690 TT during fretting due to the spinel oxides sticking into the substrate of Alloy 690 TT. Additionally, the micropitting was widened and deepened by the motion of the displaced oxide particles. The oxide particles on the surface and inside the pits were fractured to produce wear debris.