Browsing by Subject "powder flowability"

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Effect of Powder Characteristics on Tensile Properties of Additively Manufactured 17-4 PH Stainless Steel
(University of Texas at Austin, 2021) Poudel, Arun; Sotani-Tehrani, Arash; Shao, Shuai; Shamsaei, Nima
Laser beam powder bed fusion (LB-PBF) process uses metallic powders as feedstock, whose particle characteristics such as cohesion, compressibility, size distribution, etc., can vary and affect the mechanical performance of the fabricated parts. In this study, two powder batches of 17-4 precipitation hardening (PH) stainless steel (SS) supplied by EOS (Batch 1) and Carpenter Technology (Batch 2) were used to fabricate specimens using identical process parameters to understand the effects of particle characteristics on defect content as well as tensile performance of the LB-PBF specimens. Higher cohesion and compressibility as well as lower sphericity in Batch 2 resulted in specimens with higher porosity levels. During tensile testing, the higher porosity level in Batch 2 yielded lower ductility. In contrast, the microstructure was observed to be less sensitive to particle characteristics because of which the tensile strengths of the specimens were found to be comparable to each other.
Effects of Powder Reuse and Spatial Location Dependency on the Powder Characteristics and Defect Structure of Additively Manufactured Ti-6Al-4V Parts
(University of Texas at Austin, 2021) Soltani-Tehrani, Arash; Yasin, Mohammad Salman; Shao, Shuai; Shamsasei, Nima
In laser powder bed fusion additive manufacturing (L-PBF AM), different powder characteristics including particle size and morphology may yield different packing states and thus different defect content in the resulting parts. As the powder is spread by the recoater, the packing state may not be uniform on the powder bed, giving rise to location-dependent part performance. In addition, as the powder is reused (a common practice in AM industry), its characteristics continuously evolve, causing the defect content to change from build to build. This study aims to investigate the effects of powder reuse and part location on powder characteristics as well as the defect structure of the parts. Results indicate powder reuse in an L-PBF system may reduce the number of defects in the as-fabricated parts due to the superior packing state of reused powder. Part density was also found to be location-dependent, with more defects near the gas outlet.
A Method of Predicting Powder Flowability for Selective Laser Sintering
(University of Texas at Austin, 2021) Sassaman, D.; Phillips, T.; Beaman, J.; Milroy, C.; Ide, M.
This work investigates a method for pre-screening material systems for Selective Laser Sintering (SLS) using a combination of Revolution Powder Analysis (RPA) and machine learning. To develop this method, nylon was mixed with alumina or carbon fibers in different wt.% to form material systems with varying flowability. The materials were measured in a custom RPA device and the results compared with as-spread layer density and surface roughness. Machine learning was used to attempt classification of all powders for each method. Ultimately, it was found that the RPA method is able to reliably classify powders based on their flowability, but as-spread layer density and surface roughness were not able to be classified.