Sintering Study of Polyamide 12 Particles for Selective Laser Melting

Selective Laser Melting is an additive manufacturing technique, using a laser to promote the fusion followed by the solidification of a powder bed into a component. One of the most interesting topics about this process is the coalescence behavior of particles taking place in the powder bed during exposure. The coalescence of particles has been investigated in different fields of materials. Polyamide 12 (PA12) is a polymer material which is usually used in the selective laser melting process. Therefore, the characterization of the sintering behavior of PA12 powder plays an important role to improve the performance of the material and the process. The purpose of this study is to investigate the sintering process of PA12. The main goals are: to calculate the neck growth during isothermal sintering process based on the modified Frenkel ́s model; and to compare the sintering model with results from microscopic observation of PA12 powder in the hot stage. Important parameters for the sintering model such as temperature-sensitive viscosity and surface tension are measured in this paper. Furthermore, the effects of heating rate and sintering temperature on the neck growth were investigated by the microscopic observation of molten particles in the hot stage. The modeling showed a reasonable agreement with the microscopic observation in the hot stage. Specially, the effect of the heating rate on the sintering temperature was studied. It was confirmed that the sintering behavior of PA12 powder started at a higher temperature with increasing heating rate. Based on the findings from this study, a preliminary methodology for PA12 powder sintering is proposed. It provides a better understanding of the properties of the material, and more efficient use of the selective laser melting material.