New lightweight high-entropy alloy coatings: Design concept, experimental characterization, and high-temperature oxidation behaviors

Lightweight high-entropy alloy (HEA) coatings by laser cladding (LC), which combines the advantages of high- entropy alloys and laser cladding, are potential materials for high-temperature applications. Al20Cr5Fe50Mn20Ti5 20 Cr 5 Fe 50 Mn 20 Ti 5 and Al25Cr20Fe20Mn15Ti20 25 Cr 20 Fe 20 Mn 15 Ti 20 HEAs were designed, and the calculated thermal parameters were close to the Nibased alloy substrate (Inconel 718). Based on this, Al20Cr5Fe50Mn20Ti5 20 Cr 5 Fe 50 Mn 20 Ti 5 and Al25Cr20Fe20Mn15Ti20 25 Cr 20 Fe 20 Mn 15 Ti 20 HEA coatings were fabricated by LC on the substrates. The main phase structures of the two designed HEAs are the BCC + L21 1 phase, as revealed by the CALculation of PHAse Diagrams (CALPHAD). The high-temperature oxidation properties of the coatings were systematically investigated using isothermal oxidation tests. The oxidation activation energies of both coatings were 154.8 and 133.4 kJ/mol. Combined with molecular dynamics (MD) simulation, the clustering mechanism of Al and Ti elements was revealed in the formation of the L21 1 phase, whereas the high proportion of Ti elements increased the vacancy concentration, which was not conducive to oxidation resistance. Through this study, lightweight HEA coatings with excellent high-temperature performance can be designed and developed in the Al-Cr-Fe-Mn-Ti HEA system.