Porosity elimination and heat treatment of diode laser-clad homogeneous coating on cast aluminum-copper alloy

Laser cladding of homogeneous coating onto ZL205A substrate by using a high-power diode laser was investigated in order to repair casting defects of ZL205A aluminum alloy. Single and multi-layer laser cladding was carried out to optimize laser process parameters. Pores on the cross-sections of the laser-clad coatings were chain-like and distributing along the bottom of the molten pool. Lower powder feed rate and relatively higher laser power were helpful in eliminating porosity defects, and pores larger than 100 μm in diameter were successfully eliminated by optimizing laser and material parameters. The microstructure of the laser-clad coating was columnar and columnar dendrite structures with reticular Al2Cu phase precipitating in the grain boundary. The microhardness of the laser-clad coating (about 75 HV) was significantly lower than that of the substrate (about 152 HV), and could be improved to about 134 HV after suitable solution treatment afterward artificial aging treatment, which was helpful to the restoration of coatings' mechanical properties.