Show simple item record

dc.contributor.advisorTerblans, J. J.
dc.contributor.authorHarris, Richard Anthony
dc.contributor.otherSwart, H. C.
dc.date.accessioned2015-08-18T15:42:54Z
dc.date.available2015-08-18T15:42:54Z
dc.date.issued2010-06
dc.identifier.urihttp://hdl.handle.net/11660/919
dc.description.abstractEnglish: From Icarus’ mythical flight to escape Crete to manned space flight to the moon, mankind’s dream to fly has impacted this world immensely. Technological advancements made in metallurgy and alloy development has played a huge role in realizing this dream. Developing materials and superalloys with higher melting temperatures and greater strength has allowed for the design of the modern turbine jet engines. Economical and (today more than ever) environmental concerns continue to provide ample motivation for operating the engines at ever increasing temperatures, thereby improving the thermodynamic efficiency and reducing pollutant emissions. One of the most aggressive man made environments is that of the high pressure turbine section of a modern gas turbine engine. During operation, after combustion, highly oxidizing gas enters the turbine. This happens at temperatures exceeding 200 °C above the melting point of the superalloy turbine blade. Newer generations of civil aircraft will have turbine entry temperatures (TET) that will exceed 1800 K at take-off. Increased power and improved fuel consumption remains a continuing demand in modern aero-gas turbine engines as this result in an increase in TET. One strategy to achieve this goal is by coating the turbine blades with a thin film composed of alloy material. These films can be engineered to have specific heatresistant, oxidation-resistant properties. Two coating techniques that show promise in achieving these goals are pulsed laser ablation (PLD) and electron beam physical vapour deposition (EB-PVD). These techniques are investigated in this study in particular of platinum-aluminium alloys. The appearances of droplets on the thin film surface that arise due to the pulsed laser ablation technique itself are investigated. A suitable technique to minimize the appearance of these droplets by using ambient gas and ambient gas pressure is discussed. The stoichiometric transfer of material from the target to a substrate was also investigated. A lot of insight into engineering these types of coatings can be gained from computer simulations of the processes governing the diffusion of the individual elements making up the superalloy. Therefore, in this study, a chemical potential Monte Carlo (CPMC) model was developed to simulate diffusion of platinum-aluminium binary alloys. The change in microstructure during diffusion as the pure elements diffuse into each other to form an alloy with a specific composition is investigated. In the model, data structures, search algorithms and a random number generator were developed and employed in an object-orientated code 6 to simulate the diffusion of binary metals during annealing. Several simulations were performed at different compositions. The results are compared to experimentallymeasured elemental maps of EB-PVD prepared thin film samples.en_ZA
dc.description.abstractAfrikaans: Sedert Icarus se mitiese vlug om van Kretense af te ontsnap tot die meer onlangse bemande ruimte ruise na die maan het die mensdom se droom om te kan vlieg die wêreld geweldig beïnvloed en verander. Tegnologiese ontwikkeling in mettalurgie en allooi ontwikkeling het ‘n groot rol gespeel om hierdie droom te verwesenlik. Die ontwikkeling van materiale en super allooie met hoër smeltpunte en beter drywingsvermoëns het ‘n groot rol gespeel in die ontwerp van die moderne turbine vliegtuig enjins. Ekonomiese en omgewings faktore is vandag die grootste motiveerder om hierdie enjins teen selfs hoër temperature te laat werk. Hierdeur word die termodinamiese effektiwiteit verhoog en die emissie van afvalstowwe verlaag. Een van die aggresiefste mensgemaakte omgewings is in die höe druk turbine seksie van ‘n moderne gasturbine enjin. Hier word hoogs oksiderende gasse oor die turbine laat vloei teen temperature wat 200 °C hoër is as die smeltpunt van die super allooi turbine lemme. Van die nuwer generasie van siviele vliegtuie sal turbine ingangstemperature (TIT) hê wat hoër is as 1800 K wanneer die vliegtuig opstyg. Daarom is die verhoging in drywing en verbetering in brandstof verbruiking van vliegtuie ‘n vereiste in moderne gas turbine enjins. Een van die strategiëe wat gebruik word om hierdie doelwit te bereik is om die turbine lemme te bedek met ‘n dunfilm wat bestaan uit ‘n allooi material. Hierdie dun films kan so ontwerp word dat dit spesifieke hittebestande en oksidasie-bestande eienskappe het. Twee van die beddekkingstegnieke wat belowend lyk om hierdie doelwitte te bereik is gepulseerde laser deponering (PLD) en elektron bundel fisiese damp deponering (EB-PVD). In hierdie studie word hierdie tegnieke ondersoek in spesifiek op platinum-alluminium allooie. Films wat met gepulseerde laser deponering vervaardig word het klein druppel-vormige deeltjies op die oppervlakte. Hierdie druppels sowel as ‘n gepaste tegniek om die voorkoms van druppels op die dun film oppervlakte te minimeer (deur middel van die verandering van die atmosfeer druk en tipe gas in die atmosfeer) is ondersoek. Die stoigiometriese oordrag van die materiaal van die teiken na die substraat is ook ondersoek. Die stoichiometriese oordrag van materiaal vanaf ‘n teiken na ‘n substraat word ook ondersoek. Baie insig oor hoe om deklagies te ontwerp kan bekom word deur middel van rekenaar simmulasies van die diffusie prossesse in die super allooie. Gevolglik is ‘n chemiese-potensiaal Monte Carlo model (CPMC) ontwerp en gebruik om diffusie in platinum-alluminium binêre allooie te simmuleer. Met behulp van hierdie model kan die verandering in die mikrostruktuur tydens diffusie van die suiwer elemente van ‘n binêre allooi ondersoek word. In die model is data strukture, soek algoritmes en ‘n ewekansige getal generator ontwikkel en gebruik in ‘n voorwerp-geöriënteerde omgewing. Die model is gebruik om die diffusie van binêre allooie tydens verhitting te ondersoek. Verskeie simmulasies is gedoen teen verskillende element samestellings. Die resultate is vergelyk met eksperimenteel gemete element-kaarte van Pt/Al dun films wat met EB-PVD voor berei is.en_ZA
dc.language.isoenen_ZA
dc.publisherUniversity of the Free Stateen_ZA
dc.subjectThesis (Ph.D. (Physics))--University of the Free State, 2010en_ZA
dc.subjectThin filmsen_ZA
dc.subjectPulsed laser depositionen_ZA
dc.subjectPhysical vapor depositionen_ZA
dc.subjectMonte Carlo methoden_ZA
dc.subjectDiffusionen_ZA
dc.subjectSimulation methodsen_ZA
dc.subjectAmbient gassesen_ZA
dc.subjectChemical potentialen_ZA
dc.subjectDiffusionen_ZA
dc.subjectDropletsen_ZA
dc.subjectElectron beamen_ZA
dc.subjectPhysical vapour deposition (EB-PVD)en_ZA
dc.subjectMonte Carlo methoden_ZA
dc.subjectNickel based super alloysen_ZA
dc.subjectPhasesen_ZA
dc.subjectPlatinum based super alloysen_ZA
dc.subjectPulsed laser deposition (PLD)en_ZA
dc.subjectSimulationen_ZA
dc.subjectStoichiometric transferen_ZA
dc.subjectThin filmsen_ZA
dc.titleMonte Carlo simulation and characterisation of phase formation in Pt-based alloy thin filmsen_ZA
dc.typeThesisen_ZA
dc.rights.holderUniversity of the Free Stateen_ZA


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record