Additive manufacturing of wear–resistant CuCMnNiTi HEA coating through entropy reduction–phase separation technique

Copper (Cu)–based alloys with superior corrosion resistance are widely applied in industry, but their poor hardness limits their wider application. There are many researches focusing on adjusting the composition of Cu–based alloys to improve their deficiency, but the traditional “one–pot” process is difficult to form nanocrystals, which is unable to improve their hardness at the atomic level. Here, an innovative entropy reduction phase separation (ERPS) process was first proposed, and the additive manufacturing of Cu–based alloy high–entropy alloy (HEA) coating was achieved by the entropy reduction phase separation (ERPS), which included three steps of rapid prototyping, phase precipitation and enhanced phase stabilization. The CuCNiTiMn HEA coating was deposited using laser cladding (LC), and laser remelting (LR) and tempering treatment (TT) were used to release entropy and induce the phase separation at the grain boundaries, where the Cu/Ni₃Ti nanocrystalline crystals were formed. During the additive manufacturing process, the C element effectively inhibited the formation of oxides, and the Mn stabilized the Cu/Ni₃Ti nanocrystals in the CuCNiTiMn HEA coating. The hardness (624 HV_0.2) of CuCNiTiMn HEA coating is increased by 208 % compared with the commercial Cu–Ni–Ti alloy (∼300 HV_0.2) by the ERPS process, and the corresponding wear resistance (10⁻⁷ mm³/N·m) is also increased by 1000 times compared with the commercial Cu–Ni–Ti alloy (10⁻⁵ mm³/N·m). This ERPS process breaks through the hardness limit of the existing Cu–based alloys, which opens up a new idea for the application of Cu–based alloy coatings.