Microstructure and Abrasion Resistance of Thermal Sprayed Sc-doped AlCoCrFeMoW High Entropy Alloy Coatings

High entropy alloys (HEAs) represent next-generation materials consisting of five or more multi-principal elements. Doping HEAs with rare earth elements (REEs) like scandium (Sc) can significantly enhance their strength, ductility, and hardness. These improvements, induced by Sc-driven grain refinement and solid-solution strengthening mechanisms, are expected to enhance abrasion resistance, making HEAs valuable for aerospace and defence applications, such as compressor blades in aero engines and rotary blades of aircrafts. However, research on Sc-doped AlCoCrFeMoW HEA coatings fabricated through thermal spraying remains limited. This study investigates the effects of Sc doping on the mechanical/hardness and abrasion properties of AlCoCrFeMoW HEA coatings fabricated using flame spraying, a cost-effective thermal spray coating process. The Sc-doped HEA coatings were analysed for microstructure, phase formation, microhardness, and abrasion resistance by scratch testing. The findings reveal that the Sc-doped AlCoCrFeMoW HEA coatings have heterogeneous splat morphology, featuring a combination of BCC and FCC phases, along with mixed spinel and complex oxides. The BCC and spinel oxide phases are directly correlated with improved hardness and abrasion resistance compared to AlCoCrFeMoW HEA without the REE. The outcome emphasizes the potential of Sc-doped AlCoCrFeMoW HEA coatings to significantly improve the durability and protection of industrial components in extreme environments.