Effect of PEO interlayer on oxidation behavior of PEO/Cr composite coating on Zr–1 Nb alloy in 1200 °C steam

The PEO/Cr composite coating on Zr–1 Nb alloy prepared by plasma electrolytic oxidation (PEO) and filtered cathodic vacuum arc deposition (FCVAD) technologies exhibited good oxidation resistance in 1200 °C steam. The PEO interlayer was gradually dissolved by Zr substrate, and M-ZrO2 to Zr3O phase transformation occurred, but it still moderated the inward oxygen diffusion and the inter-diffusion of Cr and Zr to some extent. Moreover, the PEO interlayer suppressed the formation of ZrCr2 in Zr substrate and ZrCr2O5 secondary phases in its steam oxide layer. The PEO layer and steam oxide layer could prevent from hydrogen permeation into the Zr substrate.