Transactions of the Korean Nuclear Society Virtual spring Meeting May 13-14, 2021 Preliminary Study on the Fretting Wear Behavior of Multi-Layer Coatings for Accident Tolerant Fuel Cladding

After experiencing the Fukushima accident event, it widened the belt of consensus that high temperature oxidation and creep ballooning resistance have to be improved for considering nuclear power plant safety, which have a tolerance to severe accident [1, 2]. Generally, oxide dispersion strengthened (ODS) alloys were applied as structural materials of nuclear components, where high mechanical strength should be guaranteed at high temperatures of up to 700 °C [3, 4]. Regardless of their outstanding mechanical properties, it was difficult to manufacture these type alloys by mechanical alloying method, which dispersing Y2O3 particles in metal matrix. Recently, ODS Zr was proposed to improve the strength of conventional Zrbased alloys for enhancing accident tolerance by surface modification. However, the surface treatment by laser beam scanning changes the microstructures of fuel cladding (i.e., heat affected zone, HAZ) below ODS layer, which affects their corrosion resistances and mechanical properties during normal operations. Therefore, it is reasonable to avoid direct exposure of the ODS layer to the primary coolant during normal operations. For resolving this problem, additional arc ion plating coating (AIP) can be applied to ODS-treated Zr cladding for improving or maintaining its corrosion resistance. In this study, the reliability of the CrAl coating layer formed on the outer surface of ODStreated Zr was experimentally evaluated and compared with uncoated Zr cladding by testing scratch and fretting wear tests.