Fretting wear behavior of Zr alloy cladding tube mated with Zr alloy dimple under mixed fretting regime in simulated primary water of PWR.

• Fretting wear behavior of Zr alloy tubes under mixed fretting regime was studied. • Friction-induced microstructural evolution of worn surface was analyzed. • Fretting wear under MFR significantly promotes the oxidation of Zr alloy substrate. • The TBL layer with equiaxed oxides and the oxide layer with columnar oxides are found. The fretting wear behavior of Zr alloy cladding tube under mixed fretting regime in a high-temperature pressurized water was investigated. The main wear mechanism is adhesive wear, with characters of small-scale delamination at the center of worn area and serious delamination on the worn edge. A long crack throughout the worn area and other cracks propagated towards the substrate are observed. The cross-sectional microstructure of worn area can be divided into a thick third-body layer, thin inner oxide layer and thick tribologically transformed structure layer, and their formation mechanisms are analyzed in detail. Finally, the mixed fretting regime process and the microstructural evolution during fretting wear are discussed. [Display omitted] [ABSTRACT FROM AUTHOR]