Effect of Annealing on Microstructural and Tribological Properties of CoCrFeNiW<inf>0.3</inf> + 5 at.% C High Entropy Alloy

This study investigates the effect of annealing on the microstructural evolution, phase formation and tribological properties of CoCrFeNiW0.3 + 5 at.% C alloy prepared using atmospheric plasma spray. The annealing has a significant effect on microstructure evolution and tribological properties. The microstructure of the CoCrFeNiW0.3 + 5 at.% C alloy exhibits the lamellar microstructure. When the annealing temperature reaches 900 °C, the carbon dissolves in the chromium and forms Cr-rich carbides phase. The coarsening of grey phases is observed with the evolution of W-rich, and Cr-rich carbides as the temperature attain 1200 °C. Phase analysis results revealed that CoCrFeNiW0.3 + 5 at.% C alloy coating comprising of FCC solid solution phase, with Cr- and W-rich phase. As the annealing temperature increases from 900 to 1200 °C, more Cr- and W-rich phase evolved. The surface morphology results indicate the increase in the surface roughness value post-heat-treatment. The dilution level investigation reveals the strong metallurgical bonding between the coating and the substrate. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy reveal the formation of the oxidation state in detail. The average microhardness of the CoCrFeNiW0.3 + 5 at.% C alloy coating was found to be marginally decreased by increasing the annealing temperature, and the deposited coating microhardness was found to be 388.54 ± 14 HV0.2. The wear analysis test revealed a considerable decrease in wear resistance after heat treatment at 1200 °C. The wear volume rate of the as-deposited coating was found to be 7.88 × 10−5 mm3 N−1 m−1, and the coating annealed at 700, 900, and 1200 °C was 7.92 × 10−5, 8.02 × 10−5, 13.26 × 10−5 mm3 N−1 m−1, respectively.