b'Figure 4. Scanning transmission electron microscopy images of spray Cr-coated Zircaloy after thermal aging at 750CZircaloy) based on the inverse Kirken-dall effect. For cold spray Cr coatings, pores are more obvious inside theFigure 5. Thermal diffusivity of coating after the thermal aging, andas-deposited and aged (left) they are preferentially distributed atHiPIMS and (right) cold-spray Cr coated Zircaloy up to 700Cgrain boundaries of Cr coatings. In addition, a layer of the Laves phase formed because of the interaction of Cr coating and Zircaloy. Such Laves phase layer is consist of fine grain structure near the Cr coatings and the coarse grain near the Zr substrate, as the transmission electron microscopy image shown in Figure 4.Importantly, the formation of Laves phase layer and the larger voids formation at the interface or within the coatings do not have significant impact on the thermal diffusivity. Figure 5 shows the thermal diffusivity of Cr coated Zircaloy after thermal ageing up to 2800 hours at 750C, and very minor or no change of thermal diffusivity was observed after the thermal aging for both coatings.2023|AFC ACCOMPLISHMENTS 39'