Powder catchment in laser metal deposition

Laser metal deposition (LMD) of Inconel 718 using a coaxial nozzle is investigated by high-speed imaging. The interaction of individual powder grains with the laser induced melt pool surface and, finally, their catchment in the LMD track is observed. Powder catchment trends are explained by interpreting physical phenomena, such as the melt flow and surface tension. Distinct zones for powder catchment are categorized depending on the position of initial interaction between powder grains and the melt pool. Particles are introduced outside the melt pool ricochet and do not attach to the clad. Particles arriving outside the laser spot, onto the solidifying skin of the melt pool, are caught, and may incorporate. Some particles may remain on the clad surface as surface roughness on the built part. Particles interacting with the laser-irradiated region of the melt pool tend to move toward its center and readily incorporate into the melt. Quantitative analyses of high-speed videos are carried out to measure incorporation time of powder grains in the melt pool, their velocity, and distance traveled.