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.
Micro Void Entrapment
Meaning
Discontinuity in printed metal components can arise when small gaseous pockets are sealed during the rapid cooling of the melt pool. This defect mechanism, known as micro void entrapment, is common in laser powder bed fusion where high scanning speeds prevent dissolved gases from escaping. These tiny, scattered voids decrease the density of the final printed metal and act as internal flaws.
Void Formation
Turbulent conditions in the molten pool can draw in the surrounding shield gas or vaporize low boiling point elements from the alloy. This micro void entrapment occurs when the solidification rate of the metal surpasses the rising velocity of the bubbles, locking them in place. The resulting porosity is typically spherical and distributed throughout the printed layer.
Testing Analysis
Non-destructive testing methods such as high resolution computed tomography are used to scan components for these internal pockets. Through these scans, micro void entrapment can be measured and quantified as a percentage of total volume. Any concentration of voids above the allowable threshold requires a revision of the printing parameters to restore the component density.
Structural Consequence
Mechanical performance under cyclic loading is highly sensitive to the presence of these internal defects. Pores created by micro void entrapment act as initiation sites for microcracks, which can propagate under stress and lead to sudden structural failure. Sourcing specifications for critical components often impose strict limits on maximum pore size to prevent premature fatigue failure in the field.
For this reason, parts designed for rotating machinery are rejected if the void fraction exceeds a tenth of a percent.