Effect of Welding Current on Wear Behavior of PTA-Welded Cu35Ni25Co25Cr15 HEA Coating

High-entropy alloys (HEAs) have received increasing attention because of their excellent properties. To improve the surface hardness and wear resistance of pure Cu, a Cu35Ni25Co25Cr15 HEA coating was, for the first time, deposited on a pure Cu substrate by plasma transfer arc (PTA) welding. The welding current varied from 130 to 160 A. The microstructures and mechanical properties of the coating were investigated. The Cu35Ni25Co25Cr15 HEA coating comprised face-cubic-centered A1 (Cu-rich) and γ′ (NiCoCr-rich) phases. The coating had an apparent structural gradient with coarse grains at the interface with the Cu substrate. The bottom, middle, and top zones of the coating exhibited a fine smooth cellular structure, fine-needle structure, and long dendrites, respectively. As the welding current was increased, the dilution ratio of the coating and interfacial bonding strength gradually increased, whereas the hardness of the coating increased and then decreased. Under a welding current of 150 A, no gaps or pores appeared in the interface, and the coating exhibited good metallurgical bonding with the Cu substrate. The wear mechanisms of the Cu35Ni25Co25Cr15 HEA coating at different temperatures were also determined. Compared with pure Cu, the Cu35Ni25Co25Cr15 HEA coating exhibited excellent wear resistance, especially at high temperatures. This study paves a new way for coating on pure Cu and enhances the wear resistance of Cu components.