Melt-solid interactions in laser cladding and laser casting |
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Authors: | H Gedda A Kaplan J Powell |
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Affiliation: | 1.the Division of Manufacturing Systems Engineering,Lule? University of Technology,Lule?,Sweden;2.Laser Expertise Ltd.,Acorn Park Industrial Estate,Nottingham,United Kingdom |
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Abstract: | Experimental data in conjunction with mathematical models are used to explain various aspects of laser casting and laser cladding
by the preplaced powder method. For increasing speed, the data can be distinguished between substrate melting, dilution-free
clad bonding, bond-free casting, and poor contact breaking the melt track into spheres. Results include a thermodynamic explanation
of the wide range of process parameters over which dilution-free clad deposits can be produced, as the process switches from
heating of the insulating powder to additional cooling when the melt front reaches the substrate. Also, the interaction of
the melt pool with the powder bed is analyzed to identify why laser castings have microscopically uneven surfaces and do not
bind with the substrate. The advancement of the melt front through the powder layer is governed by heating, melting, and incorporation
of each individual grain. Although most powder grains are in the small size range for the case studied, the few particles
up to a factor 3 larger delay and therefore govern the front advancement due to much slower melting and surface tension driven
incorporation, depending on the particle size in a non-linear manner. |
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Keywords: | |
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