Modeling of the effect of powder parameters on laser cladding using coaxial nozzle

Results of a mathematical modeling of metal substrate melting and formation of a solid cladding layer by injection of powder particles through a coaxial nozzle during laser cladding are presented. The powder flow is assumed to be a mixture of a metal material (copper) and a gas (argon). The gas-powder flow from the coaxial nozzle is simulated as a mixture of two interpenetrating fluids, taking into account turbulences in the form of a standard k-epsilon model. Phase transition is simulated by means of a phase field method. Microstructure of metal crystals during solidification has been modeled. The modeling in macro-scale was carried out for different values of average density of the powder material, resulting in influence of the density on the results of the laser cladding, such as width of the heat-affected zone, width of the cladding layer, height of the cladding layer, height and width of non-melted powder. Modeling of a high-precision laser cladding has been carried out with low gas-powder flowrates. Influence of the powder size distribution and its mean density on the cladding shape is revealed. Effect of rotation of the metal flow inside the cladding is observed. For low flowrates (5 mm/s) of the carrier gas a concave shape of the layer of the non-melted powder is obtained. Influence of technological parameters (laser power, velocity and powder feed rate) on the geometry of a single-track laser clad and heat affected zone (HAZ) has been revealed. Simulations have been performed in 2D and 3D showing a good applicability of the 2D approach to describe thermal-fluid processes for the slow-moving cladding head and low gas-powder velocities that are typically used for the precise laser cladding.