Microstructural origin of physical and mechanical properties of polyamide 12 processed by laser sintering

The microstructure and properties of plastic parts made by laser sintering are known to be affected by a number of process and material parameters, whose influences are not totally elucidated yet. This study addresses the influence of the energy supplied to the powder on the microstructure and on the physical properties of sintered parts. Two different polyamide 12 powders were used. The energy density, which is derived from the laser characteristics, was shown to have a great impact on the residual porosity and on the amount of nascent particles in parts.The study of the pore size and of the porosity distribution was carried out by X-ray tomography. It is shown that the particles size distribution and the crystallisation temperature are the key parameters in the porosity formation. Finally, the influence of the microstructure and crystalline features on the mechanical properties of sintered parts is discussed.

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► Powder granulometry is the main factor influencing part porosity.
► X-ray tomography is very powerful for analysis of porosity morphology.
► Energy density supplied by laser beam has major impact on sintered part microstructure.
► Remaining nascent (unmelted) particle cores increase degree of crystallinity in parts.
► The rigidity/ductility compromise depends on final crystallinity and porosity.