Improving the high-temperature oxidation resistance of CrN coating by gradient deposition considering internal stress effects

•Deposition of gradient CrN and non-gradient CrN on Zr-4 surface.•The effect of the gradient deposition process on the residual stress and thermal stresses of CrN coatings are investigated.•The high-temperature oxidation resistance of CrN coatings under different deposition processes is discussed. In this study, two different CrN coatings were deposited on the surface of Zr-4 via a multi-arc ion-plating method using gradient and non-gradient deposition processes. The effects of two deposition processes on the high-temperature oxidation resistance and internal stress of the coatings were investigated. The microstructure and phase structure of the coatings were characterized by scanning electron microscopy, X-ray diffraction (XRD), and energy dispersive spectrometry. The high-temperature oxidation resistance of the specimens was investigated by performing thermal shock experiments and simulated loss-of-coolant accident high-temperature steam oxidation experiments. The residual stresses of both coatings during deposition were determined by XRD analysis. In addition, the thermal stresses of both coatings during the high-temperature oxidation tests were modeled and calculated. Under long-term high-temperature oxidation conditions, the gradient-deposited CrN coating exhibited improved high-temperature oxidation resistance performance than that exhibited by non-gradient-deposited CrN coating. In addition, the residual stresses of gradient-deposited CrN coating during deposition and thermal stresses during high-temperature oxidation were significantly lower than those of the non-gradient-deposited CrN coating. The results obtained herein confirm the promising potential of gradient-deposited CrN coating as an accident-tolerant fuel cladding material.