Effects of the Gas Flow and the Defocusing Distance from Laser Beam Focus on Powder-feed Laser Cladding

摘要

In this paper, the effects of the gas flow and defocusing distance from laser beam focus on powder-feed laser cladding are investigated, and a quantitative expression to describe the free surface of the molten pool is derived. The effect of transporting gas flow on the powder feed rate, and those of the transporting and shielding gas flow on the divergent angle of the gas-powder flow and the characteristics of the formed clad bead are worked out, respectively, while the other process variables being constant. The effect of gas-powder flow on the molten pool is presented as a boundary condition equation for developing the numerical model of the molten pool. The experimental results obtained at variable defocusing amount show that the negative defocusing amount rather than the positive one is suitable for laser cladding and that the defocusing amount influences the molten height below the substrate surface.