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The effect of powder properties on laser powder bed fusion of tungsten carbide-cobalt
Govender, P. 2025. The Effect of Powder Properties on Laser Powder Bed Fusion of Tungsten Carbide-Cobalt. Unpublished doctoral dissertation. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/9035c506-2d63-494e-88ba-4130103facd8
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Stellenbosch : Stellenbosch University
2025
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| access_status_str | Open Access |
| author | Govender, Preyin |
| author2 | Blaine, Deborah |
| author_browse | Blaine, Deborah Govender, Preyin |
| author_facet | Blaine, Deborah Govender, Preyin |
| author_sort | Govender, Preyin |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Govender, P. 2025. The Effect of Powder Properties on Laser Powder Bed Fusion of Tungsten Carbide-Cobalt. Unpublished doctoral dissertation. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/9035c506-2d63-494e-88ba-4130103facd8 |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/132190 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:44:23.606Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/132190 The effect of powder properties on laser powder bed fusion of tungsten carbide-cobalt Govender, Preyin Blaine, Deborah Sacks, Natasha Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering. Powder metallurgy Tungsten carbide-cobalt alloys Additive manufacturing UCTD Govender, P. 2025. The Effect of Powder Properties on Laser Powder Bed Fusion of Tungsten Carbide-Cobalt. Unpublished doctoral dissertation. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/9035c506-2d63-494e-88ba-4130103facd8 Thesis (PhD)--Stellenbosch University, 2025. ENGLISH ABSTRACT: For decades, hardmetals, also known as cemented carbides, have been crucial in making components for global industries due to their strength and wear resistance. Perhaps the most common cemented carbide are the tungsten carbide (WC) based hardmetals that are particle-reinforced metal matrix composites, where micrometer-sized WC particles are embedded within a softer metal binder, often cobalt (Co), to counter the brittle nature of WC. The conventional manufacturing of WC-Co components involves press and sinter methods, followed by heat treatments, but this is time-consuming and costly. Hence, alternative production methods are being explored. An alternative is Additive Manufacturing (AM), particularly Laser Powder Bed Fusion (LPBF), which has the potential to produce WC-Co components. However, challenges persist from studies exploring LPBF's viability for this purpose. Material integrity concerns, like cracking, delamination, balling, and low density, need resolution for successful WC-Co LPBF production. It is crucial to pinpoint appropriate printing parameters to ensure functional, high-density component manufacturing. In the realm of LPBF for WC-Co, there is a shortage of published research examining the impact of powder properties on LPBF-printed components. This study focuses on the effects of powder morphology, encompassing factors such as particle shape, size, and powder flowability, on the quality of the final LPBF components. Composite WC-Co powders with Co-content of 12 wt% and 17 wt%, respectively, designed for high-velocity oxygen fuel (HVOF) applications, are employed for LPBF of WC-Co hardmetals. These powders undergo thorough characterization to establish connections between their properties, processing parameters, and final material attributes. The research entails a comprehensive understanding of both the powders and the microstructural characteristics of WC-Co. This includes reviewing AM techniques, along with common defects. Subsequently, the powders are assessed for flow, packing properties, and spreadability. These evaluations lead to the identification of an optimal layer height for LPBF that is larger than the D50 and similar to the D90 of the cumulative particle size distribution of the powder that is being used. Notably, one of the WC-12Co powders is excluded as it exhibits poor spreadability and high cohesive nature. These techniques provide valuable insights into the selection of appropriate powders for LPBF, accounting for their characteristics and properties. A refined process for layer height selection is presented, aiming to achieve suitable layer heights for LPBF processes based on powder properties. Subsequently, printing is carried out using the recommended layer height, followed by thorough characterization of the final as-built component. To determine the effect of diffusion of impurities from the tool steel baseplate into the built material, comparison between builds on uncoated and WC-CoCr coated baseplates was conducted. Printing on supports was investigated as a means to prevent delamination that occurs with residual stresses induced during the build. The resulting as-built WC-Co samples exhibit high porosity and low densities, accompanied by substantial Co retention. The baseplate coating effectively minimizes diffusion, and components printed on supports display improved density and reduced warpage. Further refinement of LPBF printing parameters reveal that a combination of lower hatch spacing and scan speed, along with the chosen layer height, yield superior builds, as characterized by high densities and Co retention. Volume energy density (VED) is monitored in order to evaluate its link the selection of LPBF parameters. For the parameter sets that were evaluated, VED in a range from 100 – 160 J/mm3 resulted in the best combination of density with limited Co loss. However, further research is required to provide a clearer understanding of the interplay between LPBF parameters and as-built properties. Despite its porous nature, the LPBF WC-Co built material exhibits promise due to its notable Co retention, serving as a foundation for future investigations. AFRIKAANSE OPSOMMING: Hardemetale het oor die afgelope jare wêreldwyd 'n belangrike rol in die vervaardiging van komponente vir industrieë gespeel. 'n Opmerklike voorbeeld is die familie van wolframsinterkarbiede, waar wolframkarbied (WC) gebruik word as gevolg van uitsonderlike sterkte en slytasieweerstand. Mikrometergrootte WC partikels word in 'n sagter metaalbindmiddel ingelê wat die samegestelde materiaal se rekbaarheid verbeter. Kobalt (Co) dien gewoonlik as die bindmiddel of matriksmetaal met WC wat die versterkingsfase vorm. Die tradisionele metode vir die vervaardiging van WC-Co hardemetaal komponente behels drukpers- en sintertegnieke, wat deur hittebehandelings gevolg word om optimale digthede te bereik. Hierdie benadering is egter tydrowend en duur, wat die ondersoek van alternatiewe produksiemetodes aanmoedig. Een alternatief is Laagvervaardiging (LV), en meer spesifiek laser poeierbedfusie (LPBF), wat die vermoë bied om WC-Co komponente te vervaardig. Ten spyte van vorige studies wat die uitvoerbaarheid van die gebruik van LPBF vir WC-Co komponente ondersoek het, bly daar uitdagings. Hierdie uitdagings ontstaan uit probleme wat verband hou met die integriteit van die materiaal, insluitend die voorkoms van defekte soos krake, delaminering, balvorming en lae digtheid. Die suksesvolle gebruik van LPBF vir WC-Co vereis dat spesifieke LPBF vervaardigingsparameters geïdentifiseer moet word om die vervaardiging van hoë-digtheid komponente wat ten volle funksioneer te verseker. In die veld van LPBF vir WC-Co is daar 'n tekort aan gepubliseerde navorsing wat die impak van poeiereienskappe op LPBF-vervaardigde komponente ondersoek. Hierdie studie fokus op die effekte van poeiermorfologie, wat faktore soos partikel-vorm, -grootte en poeier vloei-eienskappe insluit, op die kwaliteit van finale LPBF-komponente. Samegestelde WC-Co-poeiers, met Co-inhoud van 12 gewig % en 17 gewig %, onderskeidelik, wat spesifiek vir hoë-snelheid suurstof brandstof, “high velocity oxide fuel (HVOF)” ontwerp is, word vir LPBF van WC-Co harde metale gebruik. Hierdie poeiers word omvattend gekarakteriseer om verbande tussen hul eienskappe, vervaardigingsparameters en finale materiaaleienskappe te vestig. Die navorsing behels 'n omvattende begrip van beide die poeiers en die mikrostrukturele kenmerke van WC-Co. Hierdie behels 'n hersiening van AM tegnieke, saam met verwante defekte. Daarna word die poeiers geëvalueer vir hul vloeivermoë, pakkingseienskappe en verspreibaarheid. Hierdie evaluasies lei tot die identifikasie van 'n optimale laaghoogte vir LPBF wat groter as die D50 en soortgelyk aan die D90 van die kumulatiewe partikelgrootteverdeling is. Dit is ook opmerklik dat een van die WC-12Co-poeiers van die studie uitgesluit is weens sy swak verspreibaarheid en sterk kohesie eienskap. Hierdie tegnieke bied waardevolle insig ten opsigte van die geskiktheid van poeiers vir LPBF wat betref hulle karakteristieke en eienskappe. Ten einde laaghoogtes, wat geskik is vir LPBF en gebaseer is op poeiereienskappe, te verkry, word 'n verfynde laaghoogte seleksieproses aangebied. Daarna word LPBF uitgevoer met die nuut bepaalde laaghoogte, gevolg deur volledige karakterisering van die finale komponent. Om diffusie van onsuiwerhede vanuit die basisplaat tot binne-in die opgeboude materiaal te verhoed, is die basisplaat met WC-CoCr bedek. Om delaminasie as gevolg van resspannings wat gedurende die bou-proses onstaan, te verhoed, is die insluiting van ondersteuningstrukture in die bouproses ondersoek. Die resulterende monsters toon hoë porositeit en lae digthede gepaardgaande met aansienlike behoud van Co. Die bedekking van die basisplaat is effektief toegepas om diffusie te verminder, en komponente wat op ondersteuningstrukture gebou is, vertoon verbeterde digtheid en verminderde kromtrekking. Die aangepaste vervaardigingsparameters verbeter die volume-energiedigtheid (VED), wat bevestig dat 'n kombinasie van korter interlopie afstand en laer skandeerspoed, tesame met die gekose laaghoogte, hoë kwaliteit boustukke lewer wat gekenmerk word deur hoë digthede en behoud van Co. Ten spyte van die poreuse aard van die LPBF WC-Co materiaal, hou dit belofte in weens die merkbare behoud van Co en kan dit dien as basis vir verdere navorsing. Doctoral 2025-05-29T08:38:34Z 2025-05-29T08:38:34Z 2025-03 Thesis https://scholar.sun.ac.za/handle/10019.1/132190 en Stellenbosch University xvii, 148 : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Powder metallurgy Tungsten carbide-cobalt alloys Additive manufacturing UCTD Govender, Preyin The effect of powder properties on laser powder bed fusion of tungsten carbide-cobalt |
| title | The effect of powder properties on laser powder bed fusion of tungsten carbide-cobalt |
| title_full | The effect of powder properties on laser powder bed fusion of tungsten carbide-cobalt |
| title_fullStr | The effect of powder properties on laser powder bed fusion of tungsten carbide-cobalt |
| title_full_unstemmed | The effect of powder properties on laser powder bed fusion of tungsten carbide-cobalt |
| title_short | The effect of powder properties on laser powder bed fusion of tungsten carbide-cobalt |
| title_sort | effect of powder properties on laser powder bed fusion of tungsten carbide cobalt |
| topic | Powder metallurgy Tungsten carbide-cobalt alloys Additive manufacturing UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/132190 |
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