Development of Ti6Al4V-Cr3C2 metal matrix composites using selective laser melting

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dc.contributor.advisorSacks, Natashaen_ZA
dc.contributor.authorNkosi, Nompumelelo Venessaen_ZA
dc.contributor.otherStellenbosch University. Faculty of Engineering. Dept. of Industrial Engineering.en_ZA
dc.date.accessioned2024-02-13T19:00:13Zen_ZA
dc.date.accessioned2024-04-27T02:23:26Zen_ZA
dc.date.available2024-02-13T19:00:13Zen_ZA
dc.date.available2024-04-27T02:23:26Zen_ZA
dc.date.issued2024-03en_ZA
dc.descriptionThesis (MEng)--Stellenbosch University, 2024.en_ZA
dc.description.abstractENGLISH ABSTRACT: The manufacturing of titanium alloys and metal matrix composites (MMCs) using selective laser melting (SLM) has seen a rapid growing trend over the years. This is due to the developing manufacturing technologies and the demand of attractive and improved engineering components for industrial use in aerospace, medical, and automotive sectors. The dual α-β phase titanium alloy; Ti6Al4V has found its great application in the manufacturing of turbine blades and engine components in aerospace due to its high lightweight-to-strength ratio and good combination of properties. There is always a need to further improve these mechanical properties and performance, hence the concept of the addition of metal carbides to the Ti6Al4V matrix which studies have found to have a great strength hardening effect and results in an increase in the specific strength of the composite, thus increasing the component’s life span. This study focuses on the feasibility of manufacturing metal matrix composites of the Ti6Al4V matrix reinforced with chromium carbide (Cr3C2) using selective laser melting. A scoping review was conducted to evaluate the status of SLM and its application in the manufacturing of titanium MMCs using metal carbides and it was found that the most used carbide was TiC due to its compatibility with Ti6Al4V and its attractive properties. It was also reported that the main influential SLM processing parameters were the laser power, hatch distance, scan speed and the scanning strategies which all played key roles in determining the quality of the parts. These studies were then used to choose Cr3C2 as a reinforcing material due to the high hardness, corrosion and wear resistance and comparable low density as compared to other commonly used carbides. In addition to this, Cr3C2 is a grain refiner, therefore this property aids in improving the Ti6Al4V properties using grain refinement mechanisms and since chromium is a beta stabilizer, it’s addition to Ti6Al4V will lead to the improvement of the ductility and toughness of the final MMC. The design thinking problem solving approach was used to carry out the experimental methodology. Powder characterisation for the feedstock powders was conducted to determine the flowability, apparent density, morphology, particle size and composition. The Ti6Al4V alloy samples were initially printed using the SLM machine optimised parameters, characterised and the mechanical properties were used as benchmark for the addition of the Cr3C2. Two compositions of Cr3C2 (5 wt% & 10 wt%) powders were added to the Ti6Al4V powder to make individual mixtures that were used as feedstock for SLM. The design of experiment planning was used for SLM parameter optimization of Ti6Al4V-Cr3C2 whereby the parameters were tailored, and the response of the prints was evaluated. The effect of the scanning strategy, laser power, scanning speed and hatch distance on the density, microstructure, hardness, and tensile behaviour was studied, and the optimal conditions were determined for the compositions to obtain crack-free Ti6Al4V-Cr3C2 composites. The optimal composites were heat treated and the hardness, microstructure and tensile properties were compared with as-built Ti6Al4V properties to evaluate the effect of the annealing heat treatment.en_ZA
dc.description.abstractAFRIKAANSE OPSOMMING: Die vervaardiging van titaniumlegering en metaalmatrikssamestellings (MMC's) deur gebruik te maak van selektiewe laser smelting (SLM) het n aansienlik groei in die laste paar jaar. Dit is te danke aan die ontwikkelende vervaardigingstegnologieë en die vraag na aantreklike en verbeterde ingenieurskomponente vir industriële gebruik in lugvaart-, mediese en motorsektore. Die dubbele α-β fase titanium legering; Ti6Al4V het word dikwils gebruik in die vervaardinging van turbinelemme en enjinkomponente in lugvaart as gevolg van sy lae gewig tot sterkte verhouding en kombinasie van eienskappe. Daar is altyd 'n behoefte om hierdie meganiese eienskappe en werkverrigting verder te verbeter.Die studie van byvoeding van metalkarbiede in n Ti6Al4V matriks, is al bewys on hardheid te verhoog wat die komponent se lewensduur verleng. Hierdie studie fokus op die uitvoerbaarheid van die vervaardiging van metaalmatriks-samestellings van die Ti6Al4V-matriks versterk met chroomkarbied (Cr3C2) deur gebruik te maak van selektiewe laser smelting. 'n Omvangsoorsig is gedoen om die status van SLM en die toepassing daarvan in die vervaardiging van titanium MMC's met behulp van metaalkarbiede te evalueer. Daar is gevind dat die mees gebruikte karbied TiC was as gevolg van sy verenigbaarheid met Ti6Al4V en sy aantreklike eienskappe. Daar is ook gerapporteer dat die belangrikste invloedryke SLM-verwerkingsparameters die laserkrag, skanderingspoed, vektor spasieuring en die skanderingstrategieë was wat almal sleutelrolle gespeel het in die kwaliteit van die produk. Hierdie studies is toe gebruik om Cr3C2 as 'n versterkingsmateriaal te kies weens die hoë hardheid, korrosie- en slytasieweerstand en vergelykbare lae digtheid in vergelyking met ander algemeen gebruikte karbiede. Die byvoeging van Cr3C2 sal die materiaal eienskappe van Ti6Al4V verbeter, aangesien dit die graanverfyn en die β fase stabiliseer. Wat lei tot n verbetering in elastisiteit en taaiheid van die finale MMC. Die ontwerpdenke-probleemoplossingsbenadering is gebruik om die eksperimentele metodologie uit te voer. Poeierkarakterisering vir die grondstofpoeiers is uitgevoer om die vloeibaarheid, skynbare digtheid, morfologie, deeltjiegrootte en samestelling te bepaal. Die Ti6Al4V-legeringsmonsters is aanvanklik gedruk deur gebruik te maak van die SLM-masjien-geoptimaliseerde parameters, gekarakteriseer en die meganiese eienskappe is as maatstaf gebruik vir die byvoeging van die Cr3C2. Twee samestellings van Cr3C2 (5 wt% & 10 wt%) poeiers is by die Ti6Al4V poeier gevoeg om individuele mengsels te maak wat as grondstof vir SLM gebruik is. Die ontwerp van eksperimentbeplanning (DE) is gebruik vir SLM parameter optimering van Ti6Al4V-Cr3C2 waardeur die parameters aangepas is en die reaksie van die monsters geëvalueer is. Die effek van die skanderingstrategie, laserkrag, skandeerspoed en vektor spasieuring op die digtheid, mikrostruktuur, hardheid en trekgedrag is bestudeer, en die optimale toestande is vir die samestellings bepaal om kraakvrye Ti6Al4V- Cr3C2 komposiete te verkry. Die optimale samestellings is verhit en die hardheid, mikrostruktuur en trek eienskappe is vergelyk met as-gebou Ti6Al4V eienskappe om die effek van die uitgloei hitte behandeling te ondersoek.af_ZA
dc.description.versionMastersen_ZA
dc.format.extentxv, 122 pages : illustrations.en_ZA
dc.identifier.urihttps://scholar.sun.ac.za/handle/10019.1/130679en_ZA
dc.language.isoen_ZAen_ZA
dc.language.isoen_ZAen_ZA
dc.publisherStellenbosch : Stellenbosch Universityen_ZA
dc.rights.holderStellenbosch Universityen_ZA
dc.subject.lcshMetallic compositesen_ZA
dc.subject.lcshSelective laser meltingen_ZA
dc.subject.lcshManufacturing industries -- Technological innovationsen_ZA
dc.subject.lcshUCDTen_ZA
dc.titleDevelopment of Ti6Al4V-Cr3C2 metal matrix composites using selective laser meltingen_ZA
dc.typeThesisen_ZA
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