Laser Powder Bed Fusion Processing of Ti-6Al-4V Powders with Offsize and Wide Particle Size Distributions-Process Optimization.

The considerable expense associated with metal additive manufacturing (AM), partly attributed to the high costs of raw materials, forms a significant obstacle hindering the widespread adoption and scaling of this technology. In response to this challenge, this study endeavors to explore and optimize the laser powder bed fusion (LPBF) process parameters for Ti-6Al-4V powders with offsize (45-106 µm) and wide (15-106 µm) particle size distribution (PSD) which are more cost-effective. The outcomes will be compared to those of the same alloy with a standard 15-53 µm PSD. The primary focus of this investigation revolves around two key objectives: firstly, establishing correlations between the laser powder bed fusion process parameters and the resulting density, hardness, and roughness. This objective is achieved by investigating the impact of process parameters within the context of the contour-skin-core method. Secondly, the porosity, microstructure, elemental composition, and dimensional fidelity of several components made from the offsize and wide powders were investigated, utilizing the optimized process parameters for density. To this end, an efficient multi-step experimental design and optimization process was adopted. The findings resulted in the identification of correlations between the significant process parameters and the studied responses, enabling the achievement of 98.7% density and 40.6 HRC hardness for offsize powder and 98.7% density and 40 HRC hardness for wide powder. A separate set of optimized process parameters for larger geometries produced densities exceeding 99.9% in both as-built and HIP conditions across all three powders. Additionally, the results confirmed the higher sensitivity of the roughness to powder size, with the optimized values fluctuating between 9.5 µm and 15.7 µm. Comprehensive microstructural investigation reveals no significant differences in phase evolution or grain structure resulting from the use of offsize or wide powders. This study confirms the viability of utilizing powders containing a higher portion of large particles to mitigate the costs associated with LPBF processes.