The high-temperature oxidation and mechanical properties of the Cr/Zr and CrN/Zr coating

Coating technology to modify the property of zirconium (Zr) alloy is a potential method for accident-tolerant fuel claddings. In this work, Cr-coated and CrN-coated are prepared on the surface of Zr alloy by using multi-arc ion plating technology. The effect of coatings on the high-temperature oxidation performance at 800, 1000, and 1200 degrees C has been investigated. The oxidation behavior, microstructure, and phase composition of the samples were characterized by scanning electron microscopy, atomic force microscope and x-ray diffraction analysis. The mechanical properties of the coatings before and after oxidation were examined by ring compressive and hardness tests. It is shown that all the Cr and CrN coating can effectively protect the substrate from oxidation corrosion in air due to the formation of Cr2O3, which can effectively reduce the penetration of oxygen. The thickness of the oxide layer from the side of the coating doesn't exceed to 5 mu m at 1000 degrees C, and from the uncoated side reaches to 70 mu m with pores and rough structure. Bubbles appeared on the surface of the coated samples after oxidizing at 1200 degrees C. These bubbles are located at the Cr and Cr2O3 layers. The high-temperature oxidation resistance of Cr coating at 1200 degrees C is better than that of CrN, the latter appears to crack and spall on the oxide layer. Due to the higher fracture toughness, ductility of the Cr coating and more suitable deformation compatibility, the Cr coating possesses better crack resistance than the CrN coating under mechanical loading.