Hydrogen Isotope Permeation Behavior of AlCrFeTiNb, AlCrMoNbZr and AlCrFeMoTi High-Entropy Alloys Coatings

The hydrogen permeation behavior of novel AlCrFeTiNb, AlCrMoNbZr and AlCrFeMoTi high-entropy alloy (HEA) coatings were investigated. The hydrogen permeability of HEA coatings prepared by magnetron sputtering technology were tested using gas-driven deuterium permeation and electrochemical hydrogen permeation methods. The gas-driven permeation results show that the deuterium permeation resistance of the AlCrFeTiNb coating is the worst because of the unstable structure at a high temperature. Scanning electron microscope (SEM) and X-ray Diffraction (XRD) analysis proved a loose surface morphology of the AlCrFeTiNb coating and demonstrated the formation of iron-based oxides after deuterium permeation experiments. A high content of iron in HEA coating is disadvantageous for improving the hydrogen permeability. Differently, electrochemical hydrogen permeation reveals that the AlCrMoNbZr coating could resist hydrogen permeation better in a corrosive environment (0.2 mol/L KOH solution). The AlCrFeMoTi coating was peeled off after an electrochemical hydrogen permeation test due to the poor corrosion resistance. The hydrogen behavior of HEA coatings was discussed in detail. Our study provides a promising thought on hydrogen permeation of HEA coatings.