Microstructure, mechanical properties and lead-bismuth eutectic corrosion behavior of (AlCrFeTiMo)NO and (AlCrFeTiNb)NO high entropy metal sublattice ceramic coatings

The (AlCrFeTiMo)NO and (AlCrFeTiNb)NO high entropy metal sublattice ceramic coatings were specially designed and deposited on 12Cr F/M steel substrate by means of reactive magnetron sputtering technology. The microstructure, mechanical properties and lead-bismuth eutectic (LBE) corrosion resistance of the coatings were investigated systematically. Both the coatings exhibited a single NaCl-type FCC solid solution structure. The (AlCrFeTiNb)NO coating displayed higher nanohardness (21.5 GPa), reduced elastic modulus (292.9 GPa) and compressive residual stress (-1650 MPa). The (AlCrFeTiMo)NO coating exhibited the better LBE corrosion resistance with lower oxidation corrosion rate relative to the (AlCrFeTiNb)NO coating, but some large-sized penetrating cracks appeared after corrosion. This study not only suggested that the high entropy metal sub-lattice ceramic coatings could be promising candidates for the protection of structural materials or fuel cladding in the next generation lead based reactors, but also provided basic information for designing better high entropy metal sublattice coatings, especially avoiding the inclusion of the high quantity and content of non-nitride-forming elements such as Fe.