The growing interest in increasing the wear resistance and hardness of surfaces that are in contact with abrasives or corrosive materials has inspired the development of several processes for creating protective coatings. In-situ laser cladding is one of the most promising of these processes. It enables the formation of a uniform coating by melting powder to form the desired composition from a pure powder component. In this research, pure Ti, graphite, and Fe are used for in-situ laser cladding on a steel substrate to form an Fe-TiC metal matrix composite (MMC). The effect of laser parameters on both the quality of the bonding and morphology of the in-situ-formed TiC iron-based composite clad are investigated. Results show that laser parameters play a crucial role in determining the clad quality and clad microstructure. Two combined parameters, effective energy and powder deposition density, are used to study the effect of laser parameters (i.e., laser power, scan speed and powder feed rate) on the clad properties. While results indicate that combined parameters help to determine the quality limit, laser process parameters need to be taken into account in order to study the clad microstructure. To increase the clad hardness and TiC volume fraction, C:Ti atomic ratio should increase from 45:55 to 55:45, and Fe percentages in the powder composition should decrease from 70 wt% to the 10 wt%. By varying the powder composition, a change in TiC morphology, clad microstructure and clad hardness occurs. The dilution effect is also considered in the interpretation of results. In order to estimate wear resistance, the ASTM G65-A procedure was selected to perform tests on various clad compositions. An increased wear resistance is seen when the volume fraction of TiC is increased.

The growing interest in increasing the wear resistance and hardness of surfaces that are in contact with abrasives or corrosive materials has inspired the development of several processes for creating protective coatings. In-situ laser cladding is one of the most promising of these processes. It enables the formation of a uniform coating by melting powder to form the desired composition from a pure powder component. In this research, pure Ti, graphite, and Fe are used for in-situ laser cladding on a steel substrate to form an Fe-TiC metal matrix composite (MMC). The effect of laser parameters on both the quality of the bonding and morphology of the in-situ-formed TiC iron-based composite clad are investigated. Results show that laser parameters play a crucial role in determining the clad quality and clad microstructure. Two combined parameters, effective energy and powder deposition density, are used to study the effect of laser parameters (i.e., laser power, scan speed and powder feed rate) on the clad properties. While results indicate that combined parameters help to determine the quality limit, laser process parameters need to be taken into account in order to study the clad microstructure. To increase the clad hardness and TiC volume fraction, C:Ti atomic ratio should increase from 45:55 to 55:45, and Fe percentages in the powder composition should decrease from 70 wt% to the 10 wt%. By varying the powder composition, a change in TiC morphology, clad microstructure and clad hardness occurs. The dilution effect is also considered in the interpretation of results. In order to estimate wear resistance, the ASTM G65-A procedure was selected to perform tests on various clad compositions. An increased wear resistance is seen when the volume fraction of TiC is increased.

Le procédé de projection à froid (cold spray en anglais) est un procédé fondé sur l’accélération de particules qui restent à l’état solide pour former des dépôts. L’un des forts potentiels applicatifs de ce procédé réside dans la réalisation de dépôts composites car l'incorporation des particules céramiques dans des poudres métalliques influence la microstructure et les propriétés des dépôts. Néanmoins, le principe de construction du dépôt composite n’est pas encore parfaitement établi. En conséquence, les recherches menées dans cette étude sur la fabrication de dépôts composites s’articulent autour de plusieurs domaines, à savoir :• La science des matériaux avec des études sur l’effet de la taille et de la teneur (15 vol.% - 60 vol.%) de la particule du renfort (SiC);• La mécanique des fluides avec des modélisations des vitesses des particules céramiques (SiC) et alliage d’aluminium (Al5056) et les simulations du comportement à la déformation de la particule;• Les caractérisations des dépôts avec des analyses de microstructure et de microdureté, de la cohésion du dépôt et de comportement en frottement des dépôts;Les résultats montrent que la température du gaz n'a aucun effet sur la teneur en SiC dans les dépôts mais provoque une amélioration du rendement de dépôt. La teneur en SiC dans les dépôts composites d’Al5056/SiCp augmente avec l’augmentation de la teneur en SiC dans les poudres initiales. L’ajout de SiC dans les dépôts d’Al5056 augmente la dureté et améliore la résistance à l'usure des dépôts, et puis l’amélioration dépend de la teneur en SiC dans les dépôts composites. La force de cohésion des dépôts augmente dans un premier temps avec l’augmentation de la teneur en SiC puis diminue à partir d’environ 26-27%. Les dépôts composites renforcés par SiC-67 et SiC-27 ont une teneur en SiC semblable dans les dépôts ; Pourtant la microdureté, la force de cohésion et la résistance à l'usure des dépôts formés par Al5056/SiC-67 sont supérieures à celles des dépôts construits par Al5056/SiC-27. Ce phénomène relève l’importance de l’énergie cinétique des particules renforts.Les résultats expérimentaux ont montré que les particules de SiC ne se déforment pas plastiquement mais qu’elles sont susceptibles de créer des cratères sur le substrat ou le revêtement déjà formé ou encore rebondir ou bien de s’insérer mécaniquement dans le revêtement déposé. Finalement, un modèle eulérien a été développé pour prédire la vitesse critique à partir de la morphologie de l’éjection de matière au moment de l’impact. Ce modèle a également été étendu au dépôt composite pour représenter le procédé d’empilement des particules pendant la projection. Les résultats calculés montrent la plus grande déformation des particules de la matrice grâce à l’impact des renforts. / In cold spraying, particles are accelerated in the gas jet to achieve a high velocity and deposit on the substrate with a solid state. One of potential and important applications of cold spray is realizing the composite coatings. The incorporated ceramic particles in the composite coating can greatly influence the microstructure and properties of the coatings. The objective of this thesis was to investigate factors influencing the reinforcement content in the coatings and especially the formation mechanism in cold spraying. Al5056/SiC composite coatings were prepared by cold spraying. The effect of particle size and the reinforcement content in the powders on the reinforcement content in the coatings and thus on the microstructure and the properties of the coatings were studied. A search on the particle deformation and the formation mechanism of the composite coating was also carried out by using software of fluent and Abaqus.The results show that the addition of the SiC particles in the coating increases the hardness and improves the wear resistance of the coatings. However, the cohesion strength of the coatings first increases with the increase of the SiC content in the coating and then at a certain fraction, it decreases. Moreover, under the condition of having a similar SiC content in the coating, larger SiC particles lead to better properties of the coatings.Finally, an eulerian model was used for predicting the critical velocity by the morphology of the material jet. This model has also been extended to the composite model to demonstrate the built-up process of the composite coating during cold spraying. The calculation results show that the matrix particles deform more greatly after being impacted by the reinforcements.

In order to obtain sustainable engineering systems, this research investigates surface and interface properties of metals and active nanostructured coatings. The goal is to develop new approaches in order to improve the corrosion resistance and obtain knowledge in reconstruction of worn and/or corroded surfaces. The research will focus on high carbon steels as the substrate. These materials are used in most of industries and vehicles like aircrafts and automobiles. For anti-corrosion and self-healing applications, the layer-by-layered (LBL) coatings consisting photo-catalytic materials, the corrosion inhibitor, and the polyelectrolyte will be studied. Potential dynamic tests will be carried out in order to characterize the corrosion potential and current. For wear study, we will develop a metallic composite that has several functions, such as corrosion and wear protection, refresh or reverse worn or corroded surface. Characterization techniques used include optical microscope, surface interferometer, tribometer and the hardness tester. The ultimate goal of this research is to understand several types of problems on metal surface, such as corrosion and wear, and explore the possible ways to reduce those by using active nano-structured composite coating on metal surface.

No description available.

Metallic plasma sprayed coatings are widely used in the aerospace industry for repair on worn engine components. However, the inherent defects in these coatings limit the variety of repairs and reduce the service life of the repaired parts. A potential solution to overcome this problem is to mix small amounts of inexpensive graphene oxide in the powder feedstock. The incredible strength to weight ratio of graphene oxide makes it a viable additive to improve mechanical properties of metallic plasma sprayed coatings. The powder system chosen for this research is Nickel-5Aluminum since it is a common coating for such repairs. The greatest challenge was retaining graphene oxide, which combusts at 400°C, while melting the Nickel above 1450°C using a high temperature plasma plume. Graphene oxide was successfully retained in the coatings using either of two configurations: (1) Injecting the graphene oxide powder via solution suspension separately from the metal powder, or (2) Installing a shroud on the front of the plasma gun and backfilling with Argon to inhibit combustion. The uniquely designed solution suspension configuration resulted in a higher deposition efficiency of graphene oxide while the inert shroud configuration had a more homogeneous distribution and retention of graphene oxide in the coatings. The best overall coating was achieved using the inert shroud configuration using a powder mixture containing 2% weight Edge Functionalized Graphene Oxide. Vickers microhardness increased 46% and tensile adhesion strength increased 26% over control samples. This is possible due to the mechanisms of dislocation strengthening and stress transfer previously reported in graphene oxide reinforced Aluminum composites formed by flake powder metallurgy. It was also observed that the energy released by the combustion of graphene oxide helps to uniformly melt the Nickel particles and improve the coating microstructure, allowing for more forgiving spray parameters. The methods developed and results attained in this research open opportunities for graphene oxide to be added as inexpensive reinforcements to other metallic compositions for widespread use in metal matrix composite manufacturing.

Polymer coatings are thin films of polymer deposited on different substrates for various applications. Such surface coatings can serve a functional purpose (adhesives, photographic films), protective purpose (anticorrosion), or decorative purpose (paint). Additionally, their composite coatings containing ceramic, or metal particles are often used to enhance durability, functionality, or aesthetics. Electrophoretic deposition (EPD) and dip coating are two promising methods for the fabrication of polymer and composite coatings due to the ease of fabrication, low cost, and high-volume production. EPD involves the electrophoresis of charged particles and their deposition on the electrode surface, which requires the colloidal particles to be charged in a stable suspension as a precursor solution for deposition. Many polymers cannot be deposited by EPD directly because of their charge neutrality and poor dispersion. Therefore, it is critical to develop efficient charging dispersants to modify electrically neutral polymers for their EPD. The approach was inspired by the strong solubilization power of bile acids in the human body. Two types of bile salts, cholic acid sodium salt and sodium chenodeoxycholate, and three types of biosurfactants, carbenoxolone sodium salt, glycyrrhizic acid, and 18β-glycyrrhetinic acid, which share similar structures with bile salts, were discovered for charging, dispersion, and EPD of different materials. The electrically neutral polymers (PTFE and PVDF), chemically inert materials (diamond, nanodiamond, graphene, carbon dots, carbon nanotubes and Zr-doped hydrotalcite (MHT)), and their composites can be well dispersed in suspension and deposited using these bio-surfactants as dispersants. It was found that the unique chemical structures of these biomolecules play vital roles in the surface modification and EPD of different materials. Moreover, the deposited polymer (PVDF, PTFE) and composite (PTFE-MHT) coatings can provide outstanding corrosion protection for stainless steel. The biomimetic and versatile strategy opens a way for the deposition of other electrically neutral materials through EPD. These findings also provide a promising strategy for selecting new dispersants for EPD. The deposition of high molecular weight (MW) polymers such as poly(ethyl methacrylate) (PEMA) at high concentrations in non-toxic solvents continues to be a challenge for dip coating. In this work, we firstly proposed using water-isopropanol as a co-solvent to dissolve high MW PEMA at high concentrations. It was found that water molecules can solvate carbonyl groups of PEMA and facilitate their dissolution. This method avoided the usage of toxic solvents and a long-time heating procedure for their removal. Moreover, it allows the fabrication of high-quality PEMA and composite coatings containing different flame retardant materials (FRMs), including double hydroxide LiAl2(OH)7.2H2O (LiAlDH), huntite, halloysite and hydrotalcite, through the dip coating method. A novel solid state synthesis method was proposed to fabricate LiAlDH, which is promising for the fabrication of other advanced DHs. Such composite coatings combined advanced properties of PEMA and functional properties of FRMs, such as corrosion inhibition and FR properties. / Thesis / Doctor of Engineering (DEng) / Polymer and composite coatings have been utilized for a wide range of applications due to their barrier properties, scratch and abrasion resistance, chemical resistance, and biocompatibility. Various techniques have been developed to fabricate polymer and composite coatings, such as electrophoretic deposition (EPD) and the dip coating method. However, limitations remain. EPD unitizes an electrical field to drive charged particles in a suspension toward conductive substrates to achieve film deposition. This process requires a stable suspension with charged particles, therefore, the electroneutral polymers present difficulties in their EPD. In addition, dissolving high molecular weight polymers at high concentrations in a non-toxic solvent is currently challenging, which is vital to utilize dip coating technique. The objective of this work was to develop advanced charging dispersants for EPD of electroneutral polymers and non-toxic solvents for dip coating of high molecular weight polymers. New biomimetic and versatile approaches have been developed for EPD of different electrically neutral polymers, chemically inert materials, and their composite coatings. A non-toxic co-solvent was proposed to dissolve high molecular weight polymer at high concentration for dip coating of the polymer and its composite coatings containing flame retardant materials. The results presented in this work showed the formation of high-quality films with multifunctionality and paved new strategies for further developments.

Silver is a precious metal that has traditionally been used for jewellery and money. It also possesses desirable properties such as being corrosion resistant and having good electrical conductivity, resulting in its use for industrial applications. Furthermore, it is also recognised for its tribological properties in non-cost prohibitive applications. Silver can be used as a surface coating and can be deposited using an electroplating process. The utilisation of silver as a surface coating is advantageous and sustainable, as the substrate material properties are enhanced while usage of silver is kept to a minimum. On the other hand, electroplating has been used for over a century. It is a process which is able to produce a layer of uniform and dense coating that adheres well to the substrate metal, thus modifying the properties of the substrate. It benefits from being relatively low cost and is scalable. Silver is electroplated onto stainless steel threaded compression fittings to prevent galling. Traditional silver electroplating, which contains the use of cyanide as a complexing agent in the electroplating bath, is still in use within industry, even to this day. Cyanide, in its various forms can be poisonous, toxic and even lethal, which presents a risk during the silver electroplating process. Furthermore, the toxic wastes created during the cyanide silver electroplating process are detrimental to the environment. The aim of this work is to develop a self-lubricating non-cyanide silver PTFE composite coating suitable for use in threaded compression fittings of the ferruled type. The composite can be considered self-lubricating when a concentration of 8% or more by volume of the self-lubricating PTFE substance is incorporated. My original contribution to knowledge is firstly the successful development and characterisation of a self-lubricating non-cynanide Ag-PTFE coating on stainless steel without a strike resulting in improved CoF of 0.06 from the CoF of 0.6 based on an unlubricated surface. Secondly is the application of a non-cyanide Ag-PTFE MMC for threaded compression fittings. Thirdly is the characterisation of the make-up process of threaded compression fittings through the proposed use of the torque-angle slope in assessing coating performance for threaded compression fittings during make-up. Conclusions that can be drawn for the work are that the performance non-cyanide Ag-PTFE coating exceeded the performance of the pure Ag coating made using the same non-cyanide process. Moreover, the performance of the Ag-PTFE coating shows promising results when compared to the performance of the commercial silver cyanide coating. As a viable replacement to the current silver cyanide process, the self-lubricating non-cyanide Ag-PTFE coating, will improve the working conditions and have a positive contribution to the environment. Moreover, a thinner coating with has the potential to reduce raw material usage and electroplating waste disposal costs.

Ni electrodeposition is a suitable process for producing thick deposits and thick metallic microstructures, especially for producing relatively deep micromoulds in Microsystems industry. Ni-P deposits, due to their better properties compared to Ni deposits – particularly high mechanical properties (hardness, wear resistivity), corrosion resistance, magnetic properties, a higher fatigue limit and lower macroscopic deformation – can be a very good alternative for producing Microsystems, especially for MEMS or Microengines. According to few limited literature and our primary investigations, dispersion coating and adding particle into the electrolyte can be considered as an approach in order to decrease the stress and ease the deposition of Ni-P galvanically. Although in the last decades the influence of particles embedment in the matrix by electroplating techniques have attracted the scientific interest, there are still contradictions among the research community concerning the influence of codeposited particles on the microstructure and strengthening properties of Ni-based composites coatings. In many cases, it is believed that the enhanced mechanical performance of the coatings is mainly caused by a change in the microstructure of the metal matrix and not so much by the presence of the particles themselves. In other words, the role of particle characteristics - like their nature, size and concentration - on the layer features and strengthening mechanism of electrodeposited Ni-based composite coating with different matrix is not cleared well. Furthermore, the incorporation of particles into the deposit is mainly considered as a key factor for determining the composite coatings properties. Despite of existing models of ECD, the mechanism of particle incorporation into the film under influence of different particle characteristics has not been well understood yet. Therefore, the main aim of this study is to shed light on the effect of particle characteristics (size, concentration, type) on the codeposition process, microstructure and strengthening mechanisms in Ni and Ni-P electrodeposited composite coatings.

The work deals with the preparation and mechanical properties of coated Bioglass® 45S5 based foam materials with open porosity. The samples have been fabricated applying the replication method with use of polyurethane foam. Furthermore, these samples were coated in order to increase the strength characteristics and crack resistance. Polyvinylalcohol and PVA with cellulose microfibrils have been used as coating. Besides microstructural parameters of investigated materials using the SEM images strength characteristics in compression and in tension were also quantified.