A comprehensive experiments and calculations on the Cr/Zr interface behaviour of Cr coated Zr cladding

In this study, the interface structures and adhesion behaviour between the Cr coating and Zr cladding tube substrate were studied using experimental and first-principles methods. The microstructure of the coating -substrate interface was characterised using electron backscattered diffraction (EBSD), backscattered electron, scanning electron microscopy, and transmission electron microscopy. The atomic structure of the Cr/Zr interface was evaluated using the first-principles calculations. The adhesion performance of the Cr/Zr interface was assessed based on the calculations and experimental results. Two orientation relationships, between the Cr coating and Zr cladding tube, Cr(0 0 1)/Zr(0001) and Cr(0 0 1)/Zr(01(1)over bar0) were observed using EBSD. These were in the radial direction of the Zr cladding, with the Cr(0 0 1)/Zr(0001) interface having a greater bonding strength than the Cr(0 0 1)/Zr(01(1)over bar0) interface. Additionally, a diffusion layer approximately 50 nm thick, including a mixed crystal region approximately 5 nm thick at the Cr/Zr interface, was observed. The first-principles calcu-lations attributed the strong atomic bonding strength at the Cr/Zr interface to the joint influence of covalent and ionic bonds. The Cr atoms exhibited metallic bond characteristics, while the Zr atoms exhibited covalent bond characteristics.