Abstract

BISSETT, H.  and  VAN DER WALT, I.J.. Metal and alloy spheroidisation for the Advanced Metals Initiative of South Africa, using high-temperature radio-frequency plasmas. J. S. Afr. Inst. Min. Metall. [online]. 2017, vol.117, n.10, pp.975-980. ISSN 2411-9717.  http://dx.doi.org/10.17159/2411-9717/2017/v117n10a8.

Additive manufacturing presents an attractive and cost-effective method to produce complex designs, particularly when the material of construction includes precious metals such as Pt, 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 require spherical powders to ensure a dense part or a defect-free layer. Thermal plasmas are suitable for spheroidisation of metal and alloy powders. A 15 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 flowability. 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 flow characteristics.

Keywords : additive manufacturing; laser sintering; powder metallurgy; spheroidisation; titanium; radio-frequency plasma.

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