A fundamental analysis on additive manufacturing of a cemented tungsten carbide

Van Staden, Andries Coetzee (2016-03)

Thesis (MEng)--Stellenbosch University, 2016.

Thesis

ENGLISH ABSTRACT: Cemented tungsten carbide tools, specifically tungsten carbide based alloys, have found a wide range of application fields that includes manufacturing, agriculture, and mining. These tools are used for their ability to resist the detrimental effects of several wear mechanisms, and have been developed specifically for each industrial application. Therefore, industry is consistently developing process technologies to produce customised tooling solutions using cemented tungsten carbide alloys. Additive manufacturing is chosen as a novel manufacturing process due to its superior material and process flexibility. Its flexibility in material applications, as well as its ability to produce highly complex geometries, makes additive manufacturing technologies a viable solution to the stringent requirements set by industries using cemented tungsten carbide tools. This study investigates the capability of an available selective laser melting (SLM) process to successfully produce single material layers from a cemented tungsten carbide powder. Specifically, the capability of the SLM process to fuse a tool grade cemented tungsten carbide material is investigated. The laser power, scan velocity, and hatch spacing are varied in a design of experiments. This is done in order to determine the optimum parameter combination (or processing region) to minimise the maximum surface height of each sintered layer. Samples, each produced using different parameter sets, are sintered onto a steel baseplate in an Argon environment. For each set of parameters the resultant single layer samples are analysed using microscope imaging, surface and roughness profile analyses, scanning electron microscopy (SEM) imaging and energy dispersive spectroscopy (EDS) analyses, as well as statistical analysis using the maximum surface height of each sample. The results are compared to a benchmark sample produced using a standard material and process parameter set that has been optimised to produce functional components. The results show that uniform single layers can be produced from the tool grade cemented tungsten carbide material and that the optimal parameter combination is one of high laser power, low scan velocity, and high hatch spacing.

AFRIKAANSE OPSOMMING: Wolframkarbied gereedskap het ’n wye toepassingsveld waaronder vervaardiging, landbou, en mynbou enkele voorbeelde is. Die gereedskap word gebruik vir hul vermoë om erosie en korrosie te weerstaan. Vir elke toepassing word die gereedskapstuk doelgemaak om optimale uitvoering van die taak te bewerkstellig. Soos die aanvraag na doelgemaakte wolframkarbied gereedskap toeneem, versuim tradisionele vervaardigingstegnieke om die aanvraag te bevredig. Innoverende vervaardigingstegnieke moet ondersoek word om doelgemaakte oplossings aan industrieë te verskaf wat maklik aanpasbaar is vir elke toepassingsveld. Laagvervaardiging staan uit bo tradisionele vervaardigingstegnieke vir die wye keuse van materiale, asook die buigsaamheid van die tegnieke wat tans beskikbaar is. Laagvervaardiging het reeds bewys dat komplekse geometrieë vervaardig kan word en dat hierdie komponente sonder aanpassing gebruik kan word in die afsonderlike toepassingsvelde. Dit word voorgestel dat laagvervaardiging ’n potensiële oplossing kan bied na die aanvraag vir doelgemaakte wolframkarbied gereedskap. Hierdie studie ondersoek die vermoë van ’n beskikbare laagvervaardigingstegnologie om ’n gereedskapsgraad wolframkarbied material te konsolideer in ’n enkele laag. Die moontlikheid hiervan word gemeet teen die minimum oppervlakhoogte haalbaar tydens konsolidering. Sestien 35x35mm monsters word vervaardig met verskillende vervaardigingsparameters. Hierdie monsters word gekonsolideer op ’n staal basisplaat in ’n Argon omgewing, en die laser krag, skandering spoor spasiëring, en skanderingspoed word in parameterstelle verander. Elke vervaardigingsparameterstel se monster word ondersoek met mikroskopiese fotos, oppervlak- en grofheidsprofiel analises, SEM foto en spektrum analises, asook statistiese analise. Die resultate toon daarop dat laagvervaardigingstegnologie daartoe in staat is om gereedskapsgraad wolframkarbied materiaal in enkele, uniforme lae te konsolideer. Verder is dit vasgestel dat die optimale parameter kombinasie ooreenstem met hoë laser krag, hoë skandering spoor spasiëring, en lae skanderingspoed

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