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

Abstract

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 lm 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 b 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. Keywords hydride-dehydride (HDH) powder, laser powder bed fusion (l-PBF), microstructure, Nb47Ti (Ti-53%Nb), plasma atomized (PA) powder, porosity This invited article is part of a special topical focus in the Journal of Materials Engineering and Performance on Additive Manufacturing.

Crystallographic texture configured by laser powder bed fusion additive manufacturing process: a review and its potential application to adjust mechanical properties of metallic products

“…There are some criticisms regarding the application of a simple parameter like E V in different systems. For example, the effective layer deposited (t d ) and melted (t m ) are different from lowered height (t h ), both former are associated not only with the lowering step of the bed table but with the apparent density of the powder, too [35]. Another limitation is the different effects of laser reflection and effective energy absorption in the process, along different metallic systems [36].…”

“…and metallurgical (liquidus temperature, crystalline structure, phase stability, and transformation, etc. ), as all properties influence the molten pool dynamics (see 2.2.1), including the geometry of the powder particles [48]. Therefore, it is necessary to seek more universal and representative parameters to quantify and describe, comprehensively and assertively, the relationship between procedural conditions, metallic systems, and texturing.…”

“…The present authors also obtained some results of E control by texture with Nb-48Ti alloys produced by LPBF. Figure 11 shows a comparison between the results of Young's modulus of Nb-48Ti alloy from (a) theoretical monocrystalline, (b) textured LPBF, and (c) quasi-random LPBF [17,35,37,48]. Although a reduction of only 8% in stiffness was obtained (-6 at 70 GPa), new samples and results are under evaluation.…”

Strategies and Outlook on Metal Matrix Composites Produced Using Laser Powder Bed Fusion: A Review

“…The quality and uniformity of the powder layer play crucial roles in the defect formation due to the inadequate laser-material interaction and improper filling of melt pools [84,85]. These phenomena involve issues such as insufficient melting, balling, and humping during the LPBF process [86]. Furthermore, nonspherical powders can oxidize more easily compared to the spherical powders owing to their larger surface area and irregular, low packing density [87].…”

Validation of powder layering simulation via packing density measurement for laser-based powder bed fusion

“…However, building solid, accurate, and strong parts with PBF-LB/M is only possible if the powder material properties (e.g. particle size distribution or PSD [4] and particle morphology [5]), processing parameters (e.g., laser power [6], scanning speed [6], and layer thickness [7]), and post-process heat treatments [8] are carefully optimized. This is often done by practical experiments, by comparing the mechanical properties of finished parts resulting from each IOP Publishing doi:10.1088/1757-899X/1296/1/012020 2 combination of powder material or process parameters, which is labor-intensive, time consuming, and expensive, [9][10][11].…”