Roles of Cral and Cr Coatings on the Fatigue Performance of Coated Zr4 Alloys at 400°C

Abstract

For accident tolerant fuel (ATF) cladding, there are several candidate coatings possessing superior oxidation resistance, however they may play different roles in fatigue performance. This work studied the effects of two representative ATF coatings, namely CrAl and Cr, on the fatigue life and failure mechanism of Zr4 alloy by in-situ tests at 400°C. The results revealed that, CrAl coating greatly reduced fatigue life of Zr4 alloy, whereas Cr coating significantly prolonged fatigue life. This outcome was attributed to the distinct deformation and cracking characteristics in coatings under cyclic loadings. Multiple cracks emerged prematurely in CrAl coating, accelerating the fatigue failure of the substrate. Conversely, ductile and hard Cr coating effectively constrained the plastic deformation of Zr4 substrate, inhibiting fatigue crack initiation and ultimately enhancing fatigue life. Furthermore, Cr coated Zr4 alloy by multi-arc ion plated (AIP) brought about longer fatigue life than that coated by magnetron sputtered (MS), owing to better ductility and deformation compatibility with Zr4 substrate.

Keywords: nuclear materials, coating, low-cycle fatigue, brittle cracking, ductility, Microstructure