Tribological and corrosion performance of an atmospheric plasma sprayed AlCoCr0.5Ni high-entropy alloy coating

Abstract

High entropy alloys (HEAs) are an established new class of materials exhibiting excellent mechanical and functional properties. The well-studied AlCoCrFeNi HEA has been modified to AlCoCr0.5Ni HEA in view of the latter's better oxidation resistance. The elimination of Fe and reduction in Cr content is expected to improve the HEA's corrosion and tribological performance. Thus, an AlCoCr0.5Ni HEA coating was fabricated via the atmospheric plasma spray (APS) process using mechanically alloyed (MA) feedstock. The microstructural characteristics of both the MA feedstock and coating have been investigated. The sliding wear behaviour of the HEA coating was evaluated at both room temperature and 500 °C. In addition, the electrochemical compatibility of the coating was analyzed in seawater. The microstructural results revealed that the MA feedstock was composed of BCC/B2 and FCC phases, which were retained in the HEA coating along with minor oxides. The wear resistance of the AlCoCr0.5Ni HEA coating was superior to the AlCoCrFeNi HEA coating both at room temperature and 500 °C. The high wear resistance of the coating was attributed to the formation of equal concentrations of the BCC/B2 and FCC phases. The coating exhibited a greater tendency of being cathodic (passive) than both an AlCoCrFeNi HEA coating and SS316L with identical polarization behaviour.