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G. Liedl et al.:
"Carbon dioxide laser and diode laser dispersing of TiC-Powder into aluminium substrates";
Vortrag: CLEO/IQEC, Nice/France; 10.09.2000 - 15.09.2000; in: "Proceedings CLEO/IQEC", (2000).

TiC-powder particles are embedded into AlSi7 alloys by applying the laser dispersing technique. The resulting metal-matrix-composite layers combine low density and high wear resistance. A 3 kW CO2-laser was used for the experiments together with a segmented mirror or with a parabolic mirror.
TiC-powder of different grain sizes was injected into the melt pool via an inclined nozzle by an Ar-gas jet. The zyklon-nozzle used for the experiments separates the TiC-powder form the carrier gas flow and increases the efficiency of powder dispersed by an additional focusing gas jet. Experiments show that the line-shaped focus of the segmented mirror causes an inhomogeneous powder distribution in the molten material.
However, for a circular beam spot the distribution of the TiC-powder inside the substrate is more homogeneous since the narrow size of the melt pool resulting from the line focus produced by the segmented mirror suppresses Marangoni flow. Very high powder feeding rates cause a rapid solidification of the melt and results in poor surface quality of the processed track. Cross sections of processed tracks indicate that TiC powder particles remain unchanged during laser processing which is in good agreement with theoretical results achieved previously /1/.
A 1 kW diode laser was used for further investigations and compared to the CO2-laser. Depending on the optical system, the diode laser produces a line shaped beam with a track width up to 5 mm. Although the diode laser delivers only 1 kW beam power it can be used for melting of the aluminum alloy. By carefully optimising all relevant parameters, it should be possible to replace the CO2 laser with the diode laser system and decrease fixed expenses for laser dispersing since no additional laser gases are needed.