Simulations of gas flow in gas atomisation of liquid metals and validation experiments

Abstract

The production of metal powder by gas atomisation generates feedstock for many manufacturing techniques, including hot isostatic pressing, laser cladding and, of current interest, powder bed additive manufacturing. While many thousands of alloys are commercially available in bulk form, fewer than fifty are widely available as powders suitable for additive manufacturing. This is due to difficulties in controlling droplet size distribution and avoiding particle defects. Indeed, a typical gas atomisation process that attempts to make powder for powder bed additive manufacturing achieves a yield of suitable powder below 50%. Several studies have simulated the gas atomisation process or part of it, but few validate the models directly. The current work aims to take a first step towards making a holistic and fully validated model for gas atomisation. The gas flow from de Laval nozzles under conditions similar to those used in gas atomisation has been simulated using computational fluid dynamics and experiments to validate these simulations have been performed using shadowgraphy. A validated model can be used as part of a larger model to predict the phenomena that occur in gas atomisation and thereby refine the process to improve the production yield of powders, especially for additive manufacturing.