Transient Thermal Expansion and Orifice Wear Compensation in Supersonic Argon Atomization Nozzles
Dynamic orifice compensation stabilizes supersonic argon flow to preserve fine metal powder yield across high temperature atomization runs.
Molten Metal Spray
Meaning
Pattern of liquid droplets formed by the interaction of high velocity gas and a metal stream constitutes this process state. Observing the molten metal spray allows engineers to diagnose the quality of the atomization in real time. It consists of a dense primary region and a secondary zone where droplets solidify.
The angle and velocity of this plume dictate the final shape of the powder.
Droplet Formation
Kinetic energy transfer from the gas breaks the surface tension of the liquid alloy. In the molten metal spray, the primary breakup occurs at the nozzle exit where the gas velocity is highest. Ligaments form and then snap into spherical particles due to the minimization of surface energy.
The size of these droplets is sensitive to the viscosity of the melt.
Heat Transfer
Rapid cooling occurs as the small particles travel through the inert gas environment. Heat from the molten metal spray is lost through convection and radiation at rates exceeding ten thousand degrees per second. This extreme cooling rate allows for the formation of metastable phases and fine microstructures.
It also prevents the agglomeration of particles before they reach the collection bin.
Powder Morphology
Final sphericality and surface texture are determined by the behavior of the liquid within the chamber. If the molten metal spray remains fluid for too long, particles may collide and form satellites. Controlling the flight path ensures a high yield of flowable powder for additive manufacturing.