Metal and alloy spheroidisation for the Advanced Metals Initiative of South Africa, using high-temperature radio-frequency plasmas

Abstract

Additive manufacturing presents an attractive and cost-effective method to produce complex designs, particularly when the material of construction incl ud e s precious metals such as Pi, Rh, Ir and their alloys. Layer deposition methods such as thermal spraying are also commonly used to apply protective coatings containing precious metals onto manufactured components. These methods tequite spherical powders to ensure a dense part or a defect-fiee layer. Thermal plasmas are suitable for spheroidisation of metal and alloy powders. A15 kW plasma system from TEKNA Plasma Systems Inc. was purchased in 2016. The capability of this system was investigated by performing spheroidisation experiments making use of irregular-shaped titanium metal powder at various plasma operating conditions. The resulting powders were characterised in terms of morphology, density and flowabuity. The flow characteristics of the powder were determined by means of a Hall flow test. The plasma treatment resulted in an increase in spheroidisation ratio and fraction of evaporation with increasing plasma plate power. The treated powder displayed improved Sow characteristics.