Radiation Effect in Ti-Cr Multilayer-Coated Silicon Carbide under Silicon Ion Irradiation up to 3 dpa

Abstract

Replacement of conventional Zircaloy fuel cladding with silicon carbide (SiC) fuel cladding is expected to significantly decrease the amount of hydrogen generated from fuel claddings by the reaction with steam during severe accidents. One of their critical issues addressed regarding practical application has been hydrothermal corrosion. Thus, the corrosion resistant coating technology using a Ti-Cr multilayer was developed to suppress silica dissolution from SiC fuel cladding into reactor coolant under normal operation. The effect of radiation on adhesion of the coating to SiC substrate and its microstructure characteristics were investigated following Si ion irradiation at 573 K up to 3 dpa for SiC. Measurement of swelling in pure Ti, pure Cr and SiC revealed that the maximum inner stress attributed to the swelling difference was generated between the coating and SiC substrate by irradiation of 1 dpa. No delamination and cracking were observed in cross-sectional specimens of the coated SiC irradiated up to 3 dpa. According to analyses using transmission electron microscopy, large void formation and cascade mixing due to irradiation were not observed in the coating. The swelling in the coating at 573 K was presumed to be caused by another mechanism during radiation such as point defects rather than void formation.

Evaluation of equi‐biaxial strength of thin sic coatings using ring‐on‐ring testing and digital image correlation

“…Therefore, research efforts are underway to develop surface coatings using metals or their compounds such as Ti, Cr, ZrC, CrN, TiN, and ZrN. [11][12][13][14][15] However, delamination of these coatings has been reported after neutron irradiation, primarily on account of the differences in the volume expansion induced by neutron irradiation between the metal coatings and SiC. Since the optimal approach comprises applying coatings to ceramic substrates with comparable irradiation behaviors, some research is being carried out to develop corrosion-resistant ceramic coatings, such as dense SiC deposited by chemical vapor deposition (CVD) and oxide ceramics of approximately 15 µm thick.…”

“…On the other hand, coatings for nuclear reactor‐related components must be as thin as possible to maintain thermal conductivity and neutron economy. Therefore, research efforts are underway to develop surface coatings using metals or their compounds such as Ti, Cr, ZrC, CrN, TiN, and ZrN 11–15 . However, delamination of these coatings has been reported after neutron irradiation, primarily on account of the differences in the volume expansion induced by neutron irradiation between the metal coatings and SiC.…”