Crack‐Free Tungsten Fabricated via Laser Powder Bed Fusion Additive Manufacturing

Abstract

Additive manufacturing of tungsten (W) is challenging due to its high melting point, high thermal conductivity, oxidation tendency, and brittleness from grain boundary (GB) oxides. In this study, the processing of W through laser powder bed fusion is investigated. Parts are fabricated under argon (Ar) and nitrogen (N2) atmospheres using the same processing parameters. The part produced in Ar has cracks with oxide precipitates decorating the fractured GBs. On the other hand, crack‐free W samples are produced under N2 atmosphere without any additional process modification. In both cases, the oxygen (O) content in the LPBF samples is similar to the starting powder. Interestingly, the analysis of the samples fabricated in nitrogen suggests that nitrogen is retained beyond the equilibrium solid solubility limit, while high‐resolution electron micrographs of fractured surfaces reveal reduced levels of oxides at GBs. Increased hardness for samples processed under N2 atmosphere is observed. Density Functional Theory (DFT) calculations performed to study the influence of interstitial nitrogen on oxygen diffusion in W indicated a hindrance to O diffusion from the presence of dissolved N.

Progress and Challenges of Additive Manufacturing of Tungsten and Alloys as Plasma-Facing Materials

“…Such behavior implies a moderate regime, in which desired properties may be reliably created. The creation of crack-free samples was reported by utilizing a nitrogen (N 2 ) atmosphere to reduce the oxide levels at grain boundaries, increasing the boundary cohesion [82].…”

Effect of Laser Scan Speed on Defects and Texture Development of Pure Chromium Metal Fabricated via Powder Bed Fusion-Laser Beam

“…Ramakrishnan et al recently investigated the impact of Ar and N 2 shielding gases on crack formation in pure W during the PBF-LB/M process. Rapid cooling rates inherent to PBF-LB/M led to increased N 2 dissolution and hindered O diffusion, consequently mitigating oxide formation and suppressing crack occurrence [26]. Chen et al examined the effect of incorporating 5 wt.% TaC powder into pure W to mitigate cracking.…”