Comparing Spherical and Irregularly Shaped Powders in Laser Powder Bed Fusion of Nb47Ti Alloy

Literature reports that irregularly shaped powder has lower flowability and apparent density than spherical shaped powder, factors that hinder its use in additive manufacturing, although its cost is potentially lower. In this study, four samples of Nb47Ti alloy manufactured by laser powder bed fusion from plasma atomized (PA) and hydride-dehydride (HDH) powders with different scanning strategies and interstitial element content were compared. Laser power levels of 200 W and 300 W were investigated. To keep a constant powder mass under the laser beam, the processing table displacement for samples from the HDH powder was twice larger than the 30 mu m used for samples from the PA powder procedure, due to the lower apparent density of the HDH powder. It was possible to achieve porosity levels below 1% with both powders. However, the power of 200 W generated 13% of porosity in the HDH samples. A similar microstructure formed by melt pools and cellular dendritic structure in a beta phase matrix of body-centered cubic (BCC) structure was obtained in all samples. Furthermore, the low interstitial element content of samples from PA powder resulted in lower microhardness when compared to the higher interstitial element content of samples from HDH powder.