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The Physical Vapour Deposition (PVD) magnetron sputtering process is one of the widely used techniques for depositing thin film coatings on substrates for various applications such as integrated circuit fabrication, decorative coatings, and hard coatings for tooling. In the area of coatings on cutting tools, tool life can be improved drastically with the application of hard coatings. Application of coatings on cutting tools for various machining techniques, such as continuous and interrupted cutting, requires different coating characteristics, these being highly dependent on the process parameters under which they were formed. To efficiently optimise and customise the deposited coating characteristics, PVD process modelling using RSM methodology was proposed. The aim of this research is to develop a PVD magnetron sputtering process model which can predict the relationship between the process input parameters and resultant coating characteristics and performance. Response Surface Methodology (RSM) was used, this being one of the most practical and cost effective techniques to develop a process model. Even though RSM has been used for the optimisation of the sputtering process, published RSM modelling work on the application of hard coating process on cutting tool is lacking. This research investigated the deposition of TiAlN coatings onto tungsten carbide cutting tool inserts using PVD magnetron sputtering process. The input parameters evaluated were substrate temperature, substrate bias voltage, and sputtering power; the out put responses being coating hardness, coating roughness, and flank wear (coating performance). In addition to that, coating microstructures were investigated to explain the behaviour of the developed model. Coating microstructural phenomena assessed were; crystallite grain size, XRD peak intensity ratio I111/I200 and atomic number percentage ratio of Al/Ti. Design Expert 7.0.3 software was used for the RSM analysis. Three process models (hardness, roughness, performance) were successfully developed and validated. The modelling validation runs were within the 90% prediction interval of the developed models and their residual errors compared to the predicted values were less than 10%. The models were also qualitatively validated by justifying the behaviour of the output responses (hardness, roughness, and flank wear) and microstructures (Al/Ti ratio, crystallographic peak ratio I111/1200, and grain size) with respect to the variation of the input variables based on the published work by researchers and practitioners in this field. The significant parameters that influenced the coating hardness, roughness, and performance (flank wear) were also identified. Coating hardness was influenced by the substrate bias voltage, sputtering power, and substrate temperature; coating roughness was influenced by sputtering power and substrate bias; and coating performance was influenced by substrate bias. The analysis also discovered that there was a significant interaction between the substrate temperature and the sputtering power which significantly influenced coating hardness, roughness, and performance; this interaction phenomenon has not been reported in previously published literature. The correlation study between coating characteristics, microstructures and the coating performance (flank wear) suggested that the coating performance correlated most significantly to the coating hardness with Pearson coefficient of determination value (R2) of 0.7311. The study also suggested some correlation between coating performance with atomic percentage ratio of Al/Ti and grain size with R2 value of 0.4762 and 0.4109 respectively.

A study has been undertaken with the aim of preparing appropriately functionalised polyhedral oligomeric silsesquioxane (POSS) compounds to be used in ambient-cure chemistry. Numerous epoxy-functionalised compounds have been designed and synthesised and these materials have been characterised in order to determine their chemical structure. These compounds have also been incorporated into existing polymerisation reactions to test whether these materials could be used in the protective coatings industry. A glycidyl-functionalised POSS compound was prepared and reacted with a series of amines to produce ambient-cured polymers which could be used in the coatings industry. There were also a series of experiments undertaken on these polymers to identify the processes at work and to test how they compare to industry standards. As a direct comparator to this work, another set of results was obtained with a cyclic-siloxane material incorporated into the systems in place of the POSS. A linear analogue was also tested. The reactions proved to be a success and an appropriate data-set was yielded. During the synthesis of POSS precursors there are a series of residual materials produced. These materials have also been studied in this project. It was anticipated that these would behave in a similar way to the POSS compounds however the same functionality was never achieved as had been with the POSS. Ambient-cured polymers have also been targeted from a basic hydride-functionalised POSS compound and a polybutadiene system. The appropriate reactions unfortunately never took place as anticipated but there were a series of tests undertaken to identify the processes at work. A study has also been undertaken using near-I.R. to track the curing reactions. From this data, the extent of cure could be studied and the make-up of the reaction could be investigated in more detail.

Steven Michael Ford, do hereby declare that this thesis is my own unaided work. This thesis has not been submitted in part or in full at this or any other university. This report is submitted in fulfilment of the degree of Master of Science in Engineering at the University of the Witwatersrand. / Aluminium, although often possessing adequate strength and toughness for a specific application, may be deemed unsuitable due to a less than satisfactory corrosion resistance. This unacceptable behaviour is especially prominent in the local mining industry where aluminium alloys corrode severely in the high chloride and sulphate containing waters. Of notable importance and the major motivating force for this research was the historically poor perfomance of aluminium alloy mine cages, which are suited to the task excepting for their unsatisfactory corrosion resistance. Of general importance however, is that the mining sector in South Africa represents a sizeable portion of the economy and could thus become a much greater consumer of aluminium if the metal's corrosion resistance could be improving Apart from varying the composition of the alloy, the other basic technique of increasing a metal's resistance to an environment is by applying a coating of some sort. This research looks into the use of aluminium-based metal sprayed coatings as a form of protection for various aluminium and steel substrate alloys. The purpose of a metal sprayed layer is not merely to isolate the substrate from the environment, hut also to act as a sacrificial anode at regions where the substrate is exposed. Previous work suggested that alloys of aluminium/zinc/indium produced excellent sacrificial anodes and were thus selected for this research. The zinc and indium were always alloyed with pure aluminium, with the percentage zinc varying between 0 and 12%. All the coating alloys were sprayed on a AA6261 and AA5083 aluminium alloys, a metal matrix composite and a mild steel alloy, Various electrochemical and immersion trials were then carried out in several synthetic mine waters and other corrosive media. The basic conclusion to be drawn from the results achieved is that the optimum coating for a particular substrate alloy is the one that provides the greatest potential difference between it and the substrate, while still lasting the required lifetime of the component. The reason for this is that the greater the potential difference, the better the sacrificial protection and hence the better the protection offered to any exposed areas on the surface. The fact that the coating corrodes away with time means that a balance must be found between sacrificial behaviour and required lifetime. / Andrew Chakane 2018

Student Number : 0109917P - PhD thesis - School of Process and Materials Engineering - Faculty of Engineering and the Built Environment / The aim of this project was to characterise new WC-10VC-Co powders, and to deposit WC-10VC-Co thermal spray coatings from these powders for characterisation and testing in adhesion, wear and corrosion tests. Throughout the project, the new powders and coatings were compared to commercial WC-Co powders of the same binder content and commercial WC-Co thermal spray coatings. All the powders i.e WC-10VC-Co and WC-Co powders, were produced by agglomeration (by spray drying) and sintering and characaterised by determining the sizes and size distributions of the powders' particles, the morphology, the flowability and the phase composition and grain size and size distribution of carbide grains. The vanadium carbide in the WC-10VC-Co powders occurred in the solution as the double carbide (V,W)C and the carbides present in the WC-10VC-Co powders were WC and (V,W)C. None of the starting VC was left in the powders. Coatings were deposited using high pressure high velocity oxy-fuel (HP/HVOF) spraying systems, and characterized by determining the microstructures, the phase compositions and the carbide grain sizes, as had been done for the powders. Three types of tests were done on the coatings: adhesion tests, (according to standard SNECMA 14 -008); dry abrasion, wet abrasion and slurry erosion tests; and corrosion tests, in synthetic mione water. Thermal spraying lead to some WC decarburization to W2C and eta phase, and to the formation of amorphous binder. The W2C grains from the WC decarburization formed in the amorphous binder matrix of coatings. All the coatinge were porous, but the new WC-10VC-Co coatings were more porous than the commercial Wc-Co coatings because the spray parameters had only been optimized for the WC-Co coatings. The carbide grains decreased in size by as much as 50% during decomposition. Evidence suggested that the WC grains in the coatings were subjected to different residual stresses that in the powders, probably due to the formation of the amorphous binder. Vanadium carbide in the Wc-10VC-Co coatings occurred as (V,W)C, just as in the powders, with as distribution that was reasonably homogeneous. The apparent hardness of the new Wc-10VC-Co coatings was slightly lower than that of WC-Co coatings of the same cobalt content, due to their higher porosity. The adhesion of the new Wc-10VC-Co coatings was as good as that of the Wc-Co coatings. The dry and wet abrasion resistance of the new Wc-10VC-Co coatings was better that for the Wc-Co coatings of equal Co wt%, on account of the Wc-10VC-Co coatings having a lower binder volume fraction, finer carbide grains, and (V,W)C grains. The (V,W)C grains are harder than WC grains and apparently slowed down the overall abrasion rate. In slurry erosion, the best performance of the Wc-10VC-Co coatings was as good as that of the commercial WC-Co coatings at equal cobalt mass content, due to the higher porosity of the Wc-10VC-Co coatings, apparent faster erosion of the harder but brittle (V,W)C grains, and, from what evidence appreared to suggest, generally slightly poorer erosion resistance of the fine WC grains under the test conditions used. Polishing the slurry erosion test specimens reduced mass losses in slurry erosion by factor of up to 10 compared to the unpolished specimens, and led to better erosion resistance of the WC-10VC-Co coating compared to the WC-12Co coating. The results of the tests done to investigate the corrosion properties of the coatings were conclusive. This is because the effects of cleaning procedures on mass loss after immersion corrosion were not explored, and it appeared, for some coatings, that the corrosion mechanisms in immersion corrosion could not be reproduced in electrochemical testing.

Neste trabalho são apresentados os principais conceitos relacionados às pinturas texturizadas. Foram propostas diretrizes mínimas para especificação e recebimento de pinturas texturizadas acrílicas em substratos de argamassa para fachadas de edifícios. Para o estabelecimento das diretrizes foram evidenciadas as práticas adotadas através de estudos de casos e foi realizado um estudo experimental para desenvolvimento dos principais critérios de aceitação propostos. Considera-se que a especificação técnica é o ponto de partida para assegurar que as pinturas texturizadas acrílicas atendam o uso previsto. / In this work the main concepts related to textured coatings are presented. The minimal directives are proposed for specification and act of receiving of acrylic textured coatings in renderings for buildings frontages. For the establishment of the directives the practices adopted through studies of cases had been evidenced and an experimental study was carried through for development of the main considered accepted criteria. It is considered that the technical specification is the starting point to assure that the acrylic textured coatings take care of the foreseen use.

The study addresses the coating selection for a proposed placement of a hydroturbine into the Gulf Stream. The turbine will generate energy in a similar manner to a wind turbine. The effects of biofouling and corrosion in the current project are assessed. A review of different types of traditional paint coatings is given, as well as the option for a copper-nickel alloy. Testing that should be undertaken for the coating selection is described in detail. Coating considerations are offered and discussed. Design considerations and modifications are also offered. / by Andrew Spicer Bak. / Vita. / Thesis (M.S.C.S.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.

Filmes inorgânicos de ZrO2 e filmes híbridos orgânico-inorgânicos de ZrO2-PMMA, preparados pelo método sol-gel, foram estudados como protetores contra a corrosão de aço inoxidável em meio ácido. Os sóis foram preparados a partir de uma solução submetida à irradiação de ultra-som e contendo o alcóxito metálico correspondente como precursor, álcool como solvente e ácido acético glacial como agente quelante para modificar a reatividade do alcóxito metálico. Várias concentrações de PMMA foram adicionadas aos sóis e estes foram caracterizados através de reometria, espectroscopia na região do infravermelho (FTIR), calorimetria explanatória diferencial (DSC) visando estudar a evolução de suas características morfológicas durante o envelhecimento. Os filmes de ZrO2 e ZrO2-PMMA foram depositados, utilizando-se a técnica de imersão, sobre lâminas de aço inoxidável 316L (AISI 316L), densificados a 200&#176C e o tempo de tratamento térmico foi variado de 5 a 180 minutos. Os filmes foram caracterizados por espectroscopia de reflexão especular na região do infravermelho; a morfologia, composição e textura superficiais foram determinadas por microscopia eletrônica de varredura (MEV), dispersão de energia de raios X (EDS) e perfilometria, respectivamente. curvas de polarização potenciodinâmica a 1 mVs-1 foram usadas para estudar a eficiência dos diferentes recobrimentos na proteção do AISI 316L contra a corrosão em soluções de H2SO4 0,5 mol.L-1. Os resultados mostram que os filmes híbridos ZrO2-PMMA aumentam em média 30 vezes o tempo de vida do substrato em relação aos filmes puramente inorgânicos. / ZrO2 inorganic and ZrO2-PMMA hybrids organic-inorganic films, obtained by the sol-gel method, were studied in order to determine their properties as protective layers against corrosion of stainless steel in acid media. The sol was prepared from a sonocatalyzed solution containing the appropriate metal alkoxide as precursor, alcohol as solvent, and glacial acid acetic as chelant agent to modify the reactivity of the metal alkoxide and PMMA was added into these sols. Reology, infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) were employed to determine the evolution of structural changes during aging time. The ZrO2 and ZrO2-PMMA films were deposited on stainless steel by dip-coating technique and heat treated at 200&#176C at times of heating ranging from 5 to 180 minutes. The films were characterized by FTIR reflection spectroscopy, scanning electronic microscopy, X-ray dispersive energy and profilometry to determine the surface morphology, composition and texture, respectively. Potentiodynamic polarization curves (PPC) at 1 mVs-1 were used to study the efficiency on the protection of AISI 316L against corrosion in H2SO4 0,5 mol.L-1, showing that ZrO2-PMMA increase in a factor up 30 the life time of substrate.

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