Researchers assess powder quality with triboelectric charging concept
July 22, 2024
Researchers from McGill University, Montreal, Canada, have demonstrated a new method of assessing the quality of metal powders for Additive Manufacturing using a triboelectric charging concept on using CpTi, Ti6Al4V, AlSi10Mg, IN 738, and SS 316L powders. The results were published in Scientific Reports.
In many Additive Manufacturing processes based around powder beds, such as Laser Beam Powder Bed Fusion (PBF-LB) and Binder Jetting (BJT), the quality of the spread layer – characterised by its continuity, uniformity, and packing density – must be maximised to reduce surface defects and porosity in the resultant components, .
Under the scope of ‘A method to assess the quality of Additive Manufacturing metal powders using the triboelectric charging concept,’ the authors introduced a new methodology for triboelectric charging. Modifications introduced to the GranuCharge setup included an electronic flow rate measuring tool to assess tribocharging as a function of flow rate were noted as successful.
The authors propose to measure the tribocharging behaviour at several flow rates instead of just one, because some flow rates may not indicate significant variation between two indistinguishable yet dissimilar powders, while other flow rates do. Minor variation of powder’s surface chemistry has proved to have affected the tribocharging response of the metal powders; tribocharging behaviour may not be the same even with powders having the same passivation oxide (e.g. CpTi and Ti6Al4V). The presence of negligible amounts of extra oxide, such as Al2O3, can cause considerable variation in powder tribocharging behaviour. Even a small amount of water produced a significant deviation from the expected tribocharging behaviour.
Recognising the degree of influence of moisture to the triboelectric behaviour of AM powders is paramount to assess the degradation of powder quality, explained the authors. Hence, further studies on the interaction of moisture with AM powders and how it affects their tribocharging response are recommended.
The authors have stated their intentions to evaluate other powder systems than the ones studied in this work and expand the database of tribocharging constants for AM powders, which could open the gate to use the technique to identify surface states by the tribocharging constants knowledge as an alternative to analytical techniques like XPS.
The full article is available here.
