Formation of doughnut-shaped aluminium particles in a DC non-transferred argon thermal plasma jet

In this paper, aluminium macro powders in the size range between 300 and 500 μm are processed by thermal plasma processing. A 40 kW DC non-transferred DC plasma spray torch was used to get the macro powders. The morphology and the size of the powders are discussed and the results are reported. The powders produced are doughnut shaped. The size ranges between 300 and 500 μm. The macro particle size is estimated theoretically and found to be in good agreement with experimental results. The error percentage between theoretical estimation and experimental result is about 25%. The pressure inside the particle is estimated. The pressure gradient develops the indentation on the powder surface which seems to be doughnut.