Proceedings of the
9th International Conference of Asian Society for Precision Engineering and Nanotechnology (ASPEN2022)
15 – 18 November 2022, Singapore

Investigation of Pre-thermal treatment and Surface Modification of Fine Metal Powder Feedstock on the Flowability and Agglomeration Behaviors for Binder Jetting Process

Jiemin Huanga and Su Xia Zhang

Singapore Institute of Manufacturing Technology, 73 Nanyang Drive, Singapore 637662


The use of fine powder materials in powder-based additive manufacturing processes such as binder jet printing and selective laser melting is the most preferred as fine powders can print parts with smoother surface finish with better dimensional accuracy. Furthermore, the strength of green parts printed using fine powder is enhanced as thin powder layers can improve the inter-layer bonding and facilitate binder penetration into powder layers. Fine powder particles also facilitate the sintering process due to their higher driving force for densification. However, fine SS316L powders impose greater challenges as it is more prone to agglomeration issues which affects powder flowability and end properties. Hence, this paper mainly focuses on techniques to improve the flow behavior of pure fine SS316 powders and mixtures of fine SS316L and polymethyl methacrylate (PMMA) polymeric powders for binder jetting process to produce porous metals. Two approaches will be addressed. This includes improving the powder flowability and reducing the agglomeration of fine SS316L powders by modifying the surface with different percentages of polyvinylpyrrolidone 40 (PVP 40) as well as optimizing the processing conditions for mixtures of SS316 and PMMA powders. Firstly, the flowability of pure fine 316L powders can be improved by pre-thermal treatment at 120°C and 180°C in vacuum as BFE is reduced from 344mJ to 306mJ and 222mJ respectively. Modification of SS316L fine powder surface by using PVP 40 as surfactant can effectively reduce the agglomeration of fine SS316L powders as BFE values is reduced to 267mJ when 1.5 wt% PVP40 is used in conjunction with pre-thermal treatment at 120°C. Pre-thermal treatment of as-crushed mixtures at 120⁰C significantly reduces BFE value to 142mJ as heating allows polymer to soften and bind towards SS316L powders effectively, leading to better bonding affinity between PMMA and SS316L powders to form small and uniform agglomeration.

Keywords: Fine Powders, Pre-Thermal Treatment, Surface Modification, Powder Flowability, Agglomeration.

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