Analysis of powder stream motive behavior in laser cladding based on images

In order to study the effect of powder feed parameters on the motive behavior of coaxial carrier-gas powder in laser cladding process,a digital particle image velocimetry(DPIV)test device was constructed,a special image processing software was designed for this system.Lots of tests were performed on powder transport with carrying gas.The precision of velocity vector map of the powder particles in the coaxial was determined,and distribution of powder concentration at longitudinal axis from the nozzle exit was measured with the varied powder feed rate parameters by means of DPIV.Experiments show that the velocity metal-powder particle is linear with the powder mass flow rate.The powder concentration hardly changes with various gas fluxes and constant feeding powder amount.Outside the powder mass flow rate range(0.33g/s～0.83g/s),the effect is lessened obviously.Because of the nozzle configuration of powder feed unit,powder flow has phenomena of expansion,focus and reexpansion along the nozzle exit.The focus distance and powder stream radius at the focus point also increase and locus depth decreases with increasing the gas flux.