Wear and Corrosion Resistance of HVOF-Sprayed CoCrNi Medium Entropy Alloy Coatings

Abstract

CoCrNi medium entropy alloy (MEA) coatings were prepared by high velocity oxy-fuel (HVOF) spraying. The microstructures, wear resistance in a wide temperature range, corrosion resistance in NaCl and NaOH solutions of the MEA coatings were systematically studied by SEM, XRD, friction experiment, and electrochemical corrosion test. The microstructure of HVOF coatings was uniform with FCC single-phase solid solution. As the friction temperature increased from room temperature to 200 ℃, 400 ℃, and 600 ℃, the friction coefficients, wear track depth and width, and wear volume loss of the coatings gradually decreased. And these parameters of CoCrNi coating at 600 ℃ are about 0.50 ± 0.1, (140 ± 8) μm, (2.10 ± 0.1) mm, (0.0234 ± 0.0001) g, respectively. Abrasive wear, fatigue wear and plastic deformation were the main wear mechanisms of CoCrNi coatings during the wear test at room temperature. And oxidation wear became the main wear mechanism of CoCrNi coating during the wear test at 400 ℃ and 600 ℃. E_corr and I_corr of the CoCrNi coatings in NaCl solution were approximately (-0.217 ± 0.01) mV and (0.26 ± 0.08) μA/cm², respectively. E_corr and I_corr of CoCrNi coatings in NaOH solution were approximately (-0.282 ± 0.02) and (0.04 ± 0.01) μA/cm², respectively. And the corrosion resistance of CoCrNi coatings were more superior than 45 carbon steel.