Microstructural evolution and interfacial properties of laser-cladded copper alloy on titanium alloy surfaces

Copper alloy coatings with excellent electrical conductivity, wear resistance and corrosion resistance have broad application prospects in aerospace and other fields. Laser cladding technology can achieve the preparation of high-performance coatings that are completely metallurgically bonded to the substrate. In this paper, KF320 copper alloy coatings are prepared on the surface of TC6 titanium alloy by laser cladding technology. The laser cladding process is optimized by orthogonal experiments. The microstructure and hardness distribution of the coating and the interface are analyzed, and the bonding strength of the cladding interface is evaluated by butt tensile testing. The results show that when the energy input is 44-60 J/mm, the prepared titanium alloy KF320 aluminum bronze coating is free of macroscopic cracks and has good formation density. The coating presents a dual-state region structure of “planar crystal zone + compositionally supercooled zone” along the thickness direction. At a distance of 100 μm from the top of the coating, it is mainly composed of copper phase, with phase compositions of AlCu₃ and Cu_0.84Al_0.16. With increasing depth, the content of β-Ti phase gradually increases. The average grain size of the copper phase region is about 1.96 µm, and the average grain size of the β-Ti phase is about 16.4 µm. A dense Ti₂Cu intermetallic compound transition layer is formed in situ within 10-20 μm of the cladding interface in the coating. The microhardness of the coating-substrate along the thickness direction ranges from 300HV to 375HV, with the highest hardness near the interface. The tensile test results show that the average tensile strength of the coating interface reaches 312 MPa, and the fracture morphology shows that the fracture occurs at the interface, with no fracture observed in the coating or substrate. This study provides theoretical basis and technical support for the application of laser cladding copper alloy coatings on titanium alloy substrates.