The effect of short-term annealing in an Ar environment on microstructure and adhesion property of Cr-coated Zircaloy-4 claddings

Abstract

Short-term annealing tests were conducted at 700, 900, 1100, 1200 and 1300 °C in an Ar environment to investigate the microstructure and adhesion property of the Cr-coated Zircaloy-4 cladding by arc ion plating. Scanning electron microscopy equipped with an energy dispersive spectrometer (SEM-EDS), electron backscatter diffusion (EBSD), and scanning transmission electron microscopy fitted with an energy dispersive spectrometer (STEM-EDS) were used to study the microstructural evolution between the coating and the substrate. The adhesion properties of the samples before and after short-term annealing tests were evaluated by combining scratch tests and SEM-EDS analysis. The results showed that when the annealing temperature increased, the diffusion of chemical elements became more intense, leading to the formation of an intermetallic Zr(Cr,Fe)2 layer at the interfacial region; the critical load between the coating and the substrate decreased, however, there was no sign of coating breaking or spalling during the process. Therefore, the arc ion plated Cr coating exhibited good adhesion properties below 1300 °C.