Fundamental study on direct and serial joining of spherical alumina particles with CO2 laser

Abstract

The purpose of this study is to perform laser direct and serial joining of alumina particles as the minimum unit of additive shaping and to obtain fundamentals of the joining process for achieving both the satisfactory state of bonding and the high degree of flexibility of shaping. In the experiments, spherical alumina particles were manipulated in three-dimensional space using needles and a CO2 laser beam was directed at the contact point between the particles. Direct joining was achieved under the laser power appropriate to control the melting zone. The results of cross-sectional observation and shear test for the welded joints showed that excessive laser power forms large cavities in the joints and reduces bonding strength. Nanoindentation hardness testing and Raman spectroscopic analysis revealed almost no change in microstructure of the alumina particles after joining. Serial joining of 15 particles shaped a linear chain structure with little difference in length from the estimated dimension. For fabricating fine structures with additively joined particles under the suitable laser conditions, this study provides the fundamentals of laser welding of ceramics, especially about the solidification process that critically affects joining shapes and strength.