Laser powder bed fusion of in-situ composites using dry-mixed Ti6A14V and Si3N4 powder

摘要

Herein, we report laser powder bed fusion (L-PBF) of dry-mixed Ti6Al4V + Si3N4 powder to create in-situ titanium matrix composites. The dry-mixed Ti6Al4V powder with 5 wt.% Si3N4 was processed using L-PBF at varying laser energy densities, between 44 and 133 J/mm(3), by changing the laser scan speed (400-1200 mm/s) at constant laser power of 96 W, layer thickness of 20 mu m and scan spacing of 90 mu m. The selected samples were examined for microstructural evolution, in-situ reaction products and hardness. The results showed that the in situ reaction between liquid titanium and Si3N4 forms fine TiN and Ti5Si3 reinforcements in these L-PBF processed samples. However, the irregular shape and fine size of Si3N4 reduced the feedstock flowability, and the composites could not be processed with laser energy density (E) 89 J/mm(3). The amount, distribution and size of the reinforcements were found to depend on the laser energy density. These in-situ composites exhibited high hardness of 860 +/- 49 KHN, which is 110 % higher than that of Ti6Al4V and ex-situ processed Ti-TiN and Ti-TiC composites. Our results show that the dry-mixed Ti6Al4V-Si3N4 feedstock can be processed using L-PBF but further improvement is required through adjusting Si3N4 powder attributes (size, shape) and concentration.