Laser cladding owns many advantages, such as high instantaneous heating temperature, fast cooling speed, metallurgical bonding between the coating and the substrate, small heat-affected zone and so on. Laser cladding has been used to improve the surface properties of copper and copper alloys for many years. This paper reviews the laser cladding on copper and copper alloys from the following three aspects: cladding materials, coating preparation process and functional coatings. The main problems and corresponding improvement measures for laser cladding on copper and copper alloys are summarized. Finally, the future research direction of laser cladding on copper and copper alloys are proposed.

Laser cladding is a notable metal additive manufacturing (AM). The outstanding benefit of laser cladding is that the cladding process is more flexible and it can be completed in an open environment. However, oxidation phenomenon of active metals such as titanium alloys will unavoidably clad in the open environment. To solve this problem, a three-layer annular coaxial shroud (TACS) has been designed using computational approach and evaluated by experimental data. A four-stream nozzle of gas-powder computational fluid dynamics (CFD) model was established by employing Euler-Lagrange framework to analyze the powder feeding process. Simulation results show that when the velocities of inner-layer gas of TACS and carrier gas are equal, the powder stream exhibits the best concentration within molten pool area due to the formation of the stable laminar powder stream. When the flared angle of outer-layer gas equals 45°, the vortex toroidal flow moves away from the molten pool and the argon fills in the entire cladding region to form a high-quality barrier. The optimized parameters of TACS have been applied to the practical coaxial laser cladding of Ti-6Al-4V (TC4). A single-track cladding sample with lower height to width ratio and lower wetting angle can be observed due to the flattening of the shielding gas. The oxidation is greatly reduced.

Copper and copper alloys own high thermal conductivity, electrical conductivity, good plasticity, and corrosion resistance, which are widely used in electric power, aerospace, and marine engineering. Due to low absorption rate of infrared and near infrared light, high thermal conductivity and high activity with oxygen, laser cladding of copper, and copper alloys are difficult to be conducted in air since the problems associated to cracks and voids are always hardly to be eliminated. In this paper, C-Al2O3-Cu composite powder mixed with Ni and Fe was developed to solve these problems. Use of carbon was to depress the oxidation and improve the laser absorption, while alumina was used to improve the laser absorption and mechanical strength. To improve the bonding strength between cladding layer and substrate, Ni and Fe were used. Experimental results showed that no obvious aggregation was observed and the powder showed good fluidity. The tensile strength of the cladding layer is 406.7 ± 0.1MPa which is about 1.7 times higher than that of pure copper substrate, and the tensile fracture of the cladding layer revealed microporous aggregation fracture due to the existence of Al2O3 in the cladding layer.