Argon Gas Consumption and Breakup Dynamics in Tool Steel Atomization
Specific gas consumption and nozzle tip pressure determine liquid breakup efficiency and final yield in tool steel atomization.
Internal Argon Porosity
Meaning
Small spherical voids filled with inert gas can reside within individual powder particles generated by gas atomization. This microstructural defect is termed internal argon porosity, and it directly influences the density of components fabricated using laser powder bed fusion. When the particles melt under the laser beam, the trapped gas may fail to escape, leaving tiny pockets of gas in the finished part.
Void Formation
Gas becomes trapped when the turbulent molten metal stream encapsulates the atomizing gas during droplet formation. This internal argon porosity is sealed inside as the droplet cools and solidifies before the gas can migrate to the surface. It is more common in larger powder particles where cooling rates are slower than in the finer fractions.
Quality Impact
Sourcing high quality alloys requires keeping this defect to a minimum because it directly affects the fatigue strength of the consolidated metal. The remaining pores from internal argon porosity act as stress concentration points under cyclic loading, which can lead to premature component failure. This issue is particularly critical for aerospace and medical applications where component reliability is paramount.
Processing Correction
Laser parameters such as power and scan speed are optimized to encourage the release of these trapped gas bubbles during the melting process. Additionally, hot isostatic pressing of the printed parts can squeeze these voids closed, though the compressed gas may re-expand if the part is later heated. Minimizing the initial gas inclusion in the feedstock powder remains the most reliable strategy.
Sourcing managers therefore insist on scanning electron microscopy or computed tomography of incoming powder lots to verify low gas entrapment before production starts.