Browsing by Author "De Waal, A"

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    Critical powder characteristics for high quality laser powder bed fusion
    (Stellenbosch : Stellenbosch University, 2024-02) De Waal, A; Blaine, DC; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.
    ENGLISH ABSTRACT: The acceptance of Additive Manufacturing (AM) as a reliable manufacturing technology in South Africa and globally, is still limited. This is due to concerns about replicability and variations in quality. Efforts to enhance AM standards aim to address these challenges by focusing on understanding raw metal materials. Characterizing and comprehending powder materials pose significant challenges for the AM community, especially in technologies utilizing a powder bed. Powder behaviour during spreading is a relatively new research area that is not fully understood. Academia and industry practitioners are actively exploring these concepts to enhance AM's quality, reliability, and replicability. This research aims to identify and validate critical metal powder characteristics that include the powder morphology, particle size distribution, moisture content, flowability and various densities of the powder, and their relation to efficient powder spreadability characteristics that effectively describe the powder layer quality. Furthermore, the relationship of these characteristics to consistently building high-quality final parts using the AM technique known as laser-powder bed fusion (L-PBF) must be established. The results obtained in this project aid the Collaborative Programme in Additive Manufacturing (CPAM) strategy that is focused on identifying L-PBF as a reliable and accepted manufacturing technique in South Africa as well as globally. Standardised and customised powder characterisation testing was conducted on different powders that included two spherical powders that are designed for LPBF, namely, commercially pure titanium (CP Ti) and Ti-6Al-4V, as well as a CP Ti powder that is produced by the hydride-dehydride process (HDH), that displays an angular particle shape and is not typically used for L-PBF. The results from the powder characterisation experiments successfully identified critical powder characteristics that influence powder spreadability and, consequently, the as-built part quality. Thus, the impact of powder characteristics on the spreadability of the powder and the resultant direct effect on the powder layer quality is demonstrated, emphasizing the importance of aligning spreading parameters with the critical powder characteristics that include powder flowability, packing ability, and settling rate for consistent, high-quality powder layers. A criteria system that validates whether a powder is suitable for L-PBF, based on the powder characteristics, was identified, and used to determine whether a mixture of the spherical and HDH CP Ti powders is useable for L-PBF as a more cost-effective solution. It was determined that a 90:10 mass ratio mixture of the spherical to HDH CP Ti powders delivered suitable spreadability results for L-PBF.