Microstructure evolution of a Cr-Cr/Mo coated Zr alloys in inert gas and steam environment at high temperature

The Cr/Mo multilayer coating was applied as a diffusion barrier for Cr-coated Zr alloys. The barrier effect and eutectic resistance of the Cr/Mo multilayer were evaluated by annealing the samples up to 1400 degrees C in an inert gas and steam environment. The microstructure at the interface between the Cr/Mo multilayer and Zr substrate was analyzed by spherical aberration corrected transmission electron microscope (AC-TEM). After high temperature annealing, an interlayer composed of Cr-Mo-Zr mixed phases formed between the coating and Zr substrate. The atomic-resolution EDS revealed that the proportion of Cr, Mo, and Zr in the interlayer was 4:2:3. The growth of the Cr-Mo-Zr interlayer obeyed a parabolic law. The consumption rate of the outer Cr coating was compared to that of Cr coated Zr alloy samples without a Cr/Mo barrier layer. Results show that the Cr/Mo interlayer successfully reduced the Cr-Zr inter-diffusion and eutectic reaction.