Effect of Ti content on the microstructure and properties of AlCoCrFeNi2.1 coatings fabricated by laser directed energy deposition

The influence of Ti content on the microstructure, mechanical properties, and corrosion behavior of Ti x AlCoCrFeNi 2.1 ( x = 0.1, 0.15, 0.2) high-entropy alloy (HEA) coatings, fabricated via laser-directed energy deposition (L-DED) on 2Cr13 steel, was systematically investigated. The results show that Ti addition significantly alters the solidification pathway, transitioning the microstructure from a lamellar eutectic (Ti0.1) to an equiaxed FCC and BCC dual-phase structure (Ti0.2). These microstructural changes, along with an increasing fraction of BCC and the presence of nano-precipitates, lead to a continuous enhancement in both hardness and wear resistance. As a result, the wear rate ( WR ) of the coating can be reduced by up to a 65.1% compared to the substrate. Among the studied HEA coatings, the Ti0.1 coating exhibits the best corrosion resistance, while coatings with higher Ti content exhibit lower corrosion resistance. The Ti0.15 coating achieves an optimal synergy between wear and corrosion properties. Compared to the substrate, its WR is reduced by 56.6%, and it maintains a corrosion rate ( CR ) that is nearly an order of magnitude lower than that of the substrate. Overall, our findings suggest that moderate Ti content optimally balances the wear and corrosion resistance of the HEA coatings by tailoring a dual-phase structure while suppressing Laves phase formation.