Microstructure and Mechanical Properties of the Plasma-Sprayed and Cold-Sprayed Al_0.5CoCrFeNi₂Ti_0.5 High-Entropy Alloy Coatings

In this study, Al_0.5CoCrFeNi₂Ti_0.5 high-entropy alloy (HEA) powders were prepared by the gas atomization method. The sieved powders with particle sizes of 10-60 and 60-120 µm gas-atomized powders were chosen for further analysis and coatings’ application processes. The as-obtained powders possessed spherical shape and uniform element distribution with an initial FCC structure with a minor BCC phase. The as-atomized powders were annealed at 1000 °C temperature for varying durations and characterized to determine their stable state properties. After annealed at 10000 °C, the metastable BCC phase disappeared and Al_0.5CoCrFeNi₂Ti_0.5 transformed into solid-solution FCC matrix with minor BCC precipitates. The Vickers hardness of the plasma-sprayed coatings showed an increasing trend from 285.3 to 396.7 HV as the current was raised from 500 to 750 A, respectively. Cold-sprayed coatings were performed on both carbon steel and aluminum alloy AA 6061, and their properties were analyzed. The obtained hardness of 426.6 HV was about 10% higher than the plasma-sprayed coatings. Plasma-sprayed coating properties can be varied with plasma power and size of the powder particles. Mechanical locking effect enhanced the bond strength in cold-sprayed AA 6061 compared to carbon substrate. Improved mechanical properties in this alloy were due to precipitation hardening after titanium addition.