On the thermal stability and oxidation resistance of Zr/X(Cr, Ni, Si) multilayer structure

Abstract

The application of multilayer coatings in the field of nuclear-grade zirconium alloy protection has attracted much attention. However, the phenomenon of element diffusion between layers at high temperature has not been systematically studied. In this work, by selecting specific elements X (Cr, Ni, Si), the stability and oxygen barrier properties of the multilayer film coupled with Zr layer were investigated. The key characteristic indicators were clarified, including grain boundary effect, oxygen diffusion coefficient and Zr/X inter-diffusion ability. Zr/Si multilayer system outstripped others with excellent oxidation resistance, and only the surface Zr layer was completely oxidized at both 400 °C and 700 °C in air. At hot steam environment of 400 °C/10.3 MPa, the formation of a thin amorphous Zr-Si-O layer and an amorphous silicon oxide layer guarantee good oxygen barrier effect and greatly reduce the oxygen partial pressure at oxidation front.