Effects of nitrogen content on the phase composition and high-temperature steam oxidation resistance of Cr0.5Al0.5Nx (x = 0.33, 0.81, 1.23) coatings on Zry-4 alloy.

Cr 0.5 Al 0.5 N x (x = 0.33, 0.81, 1.23) coatings were deposited on Zry-4 alloy using magnetron reaction sputtering technique to investigate their application as accident-tolerant fuel materials. The effects of nitrogen (N) content on the phase composition and high-temperature steam oxidation resistance of the coatings were systematically investigated. With the increasing N content, the phase composition of the coatings is mainly transformed from Cr(Al) to the cubic- CrAlN phase, which may be due to the formation of a greater number of Cr N bonds and Al N bonds. The high-N content of the Cr 0.5 Al 0.5 N x coating can significantly enhance the high-temperature steam oxidation resistance of zirconium alloy. Compared to the bare Zr alloy, the weight gain oxidation of the Cr 0.5 Al 0.5 N 1.23 coating is reduced by 45 % after oxidation at 1200 °C for 1 h. The oxide layer thickness of the bare Zry-4 alloy is as high as 350 μm, while the oxide layer thickness of the Cr 0.5 Al 0.5 N 1.23 coating is only about 12 μm. The complex oxide layer structure and an internal continuous Al 2 O 3 layer are formed, effectively preventing the inward diffusion of O2−. In addition, with the increase of N content in the coatings, the degree of interdiffusion between the coating and the substrate is weakened. The formation of α-Zr(N) layer in the Cr 0.5 Al 0.5 N 1.23 coating significantly inhibits the interdiffusion between the coating and the substrate. • The phase composition of Cr 0.5 Al 0.5 N x coatings is mainly transformed from Cr(Al) to cubic -CrAlN with increasing N content. • The oxide layer structure and a continuous Al 2 O 3 layer of Cr 0.5 Al 0.5 N 1.23 coating prevented the inward diffusion of O2−. • The α-Zr(N) layer in the Cr 0.5 Al 0.5 N 1.23 coating significantly inhibits the interdiffusion between coating and substrate. [ABSTRACT FROM AUTHOR]