Numerical simulation of transport phenomena, formation the bead and thermal behavior in application to industrial DMD technology

• Numerical and experimental investigations for DMD coaxial nozzle were conducted.
• The model combines transportation and heating of a powder and cladding a bead.
• The influence of the cladding parameters on individual beads is studied.
• Two key modes of the laser cladding process are determined.
• Comparison of calculated bead showed good agreement with the experiments.

The paper presents the results of theoretical and experimental investigations of the laser cladding with TRUMPF DMD 505, which enables to implement the industrial-level coating technology. The physical–mathematical model is proposed to describe and numerically simulate the processes; the model combine powder transportation and heating and formation of bed-like cladding in the conjugate statement. Special attention is paid on the simulation of gas dynamics of a triple coaxial nozzle, peculiarities of gas-disperse jet formation and optimal powder supply into the melt pool. Thermal processes in the bead and substrate are considered on the base of the conductive heat transfer with movable boundaries, phase changes, and condition of kinematic consistency of clad surface points (melt thermal convection is beyond our consideration). The influence of the governing cladding parameters on the linear sizes of individual beds from Stellite 6 alloy on a steel substrate is studied. Comparison of calculated bead profiles and full-scale experiment data showed good qualitative and quantitative agreement. The proposed model is self-consistent and can be applied to optimize the regime parameters of the laser cladding of materials.