KEYWORDS: Particles, Cladding, Gas lasers, Metals, Thermal modeling, Motion models, High power lasers, Laser applications, Laser processing, Control systems
The metal powder flow is sprayed by a coaxial nozzle with carrying gas in laser cladding, and the
powder particles are radiated to be melt metal by high power laser beam. The melting metal enters the
melting pool on the substrate which is radiated by the same laser beam. The cladding layer forms, when
the melting metal cool down. It is crucial to study the influences of different process parameters on the
motional and thermal behavior of moving powder particles. In this paper, 2D model about a moving
particle's motional and thermal behavior were established. Results show that the increasing mode of
the velocities of a powder particle and the carrying gas depends on their initial velocity; the maximum
value of the particle velocity appears in the middle of the nozzle exit; and the temperature of the
particle rises rapidly and then falls due to the relationship between cold gas, the variation of laser
intensity and its velocity and so on. The results are very helpful to design the nozzle and to select
process parameters in coaxial laser cladding.
A numeric model of velocity and concentration distribution of shield gas-metal powder two phases flow field output by
nozzle in laser cladding is established, and it is calculated by FLUENT software. In this model, the influences of
momentum and mass transmission in the two phases flow are taken into consideration. The analysis on metal powder
flow field velocity and concentration distribution with different process parameters (nozzle exit width w, initial gas flow
velocity u and initial powder concentration c at nozzle entrance, angle of inward and outward wall of nozzle α, Φ) is
conducted. The calculated results show that w mainly affects concentration and velocity magnitude, u mainly affects the
focused position and velocity magnitude, c mainly affects concentration magnitude, α and Φ mainly affects the focused
position and concentration magnitude. Under the process parameter conditions: w=1mm, c=0.1, u=3m/s,α=82 ° ,
Φ=68.5°, the same flow field is measured with DPIV technique. The calculated result agrees with the measured result,
which indicates that the established model is reliable. The model can be used to understand the influences with different
flow field process parameters and further design the nozzle size.
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