'The MTC have completed the most comprehensive characterisation of powders I have ever seen'
David Jarvis, Head of Strategic and Emerging Technologies, ESA
Additive manufacturing (AM) uses powder as its raw material feedstock. It is known that the powder characteristics will impact on the quality of the final AM components. Historically characterisation of metal powders has been limited to rudimentary techniques such as sieving and flow through an orifice. These techniques offer limited opportunity to develop powder specifications that are adequate for AM process control. Furthermore, sourcing AM powders is a non-trivial task due to the multiple supply chain options available. The challenge here was to assess the quality of powders, atomised in Europe, using advanced powder characterisation techniques, to select the most appropriate suppliers and to develop new specifications for enhanced control over powders used in AM technologies.
Within the FP7 European funded AMAZE II programme the MTC were tasked with completing a market assessment to identify European powder suppliers capable of producing the required alloy compositions. Procured powders were submitted to the MTC’s advanced powder characterisation laboratory for analysis to fully quantify the differences between powders procured from various suppliers. The analysis was based on; (1) Bulk packing and flow behavior, (2) Particle size and morphology, and (3) Chemical composition. To ensure equivalent testing conditions all samples were conditioned prior to testing and testing was conducted in a relative humidity controlled environment.
Assessment of powders procured from various European powder suppliers has demonstrated that powder characteristics do vary from supplier to supplier even when powders are atomised via the same method and supplied as ‘nominally’ the same grade. The initial powder characterisation work was used to inform the development of powder specifications. All incoming powders, which are accepted for AM processing, will have been quality assured against these specifications ensuring that a consistent raw powder feedstock is used throughout the programme. The powder characterisation results were fed back to powder suppliers allowing them to learn from the analysis
'If we are unaware of the differences that can exist between powders which are ‘nominally’ the same grade and we do not perform adequate quality control testing on virgin powders then we cannot guarantee control over our AM processes'
Jason Dawes, Particulate Engineering Group Technology Leader, MTC