Understanding mechanical and electrochemical performance of plasma sprayed AlCoCr0.5Ni high-entropy alloy coatings

High entropy alloys (HEAs) are a new generation of materials with unique characteristics and properties have demonstrated diversified technological potential. Recently, thermal spray in conjunction with HEAs has shown promising capabilities of being applied in different extreme engineering environments. The present work investigates the microstructural, mechanical, wear and electrochemical behaviour of the plasma sprayed AlCoCr_0.5Ni HEA coating. The corresponding HEA was fabricated by means of mechanical alloying followed by spraying through atmospheric plasma spray (APS) process. The wear behaviour of the coating was evaluated using the pin-on-disk method, both at room temperature and 500 °C. Microstructural and compositional changes were investigated by XRD, SEM and EDS. The electrochemical performance of the coating was analysed using potentiodynamic polarization method in 3.5wt% NaCl solution. The microstructural results indicated that coating was intact, spallation free and acquired lamellar, composite type multi-phase structure. More importantly, the coating exhibited superior high-temperature wear performance as compared to room temperature, inferring phase stability at high thermal loads. Plasma sprayed AlCoCr_0.5Ni HEA coating displayed similar polarization behaviour as SS316L substrate, however, corrosion resistance was marginally lower than that of SS316L.