Advanced Materials Research Vols. 264-265

Abstract: Erosion due to solid particles impact has a detrimental effect on the performance of components used in various applications. Hard facing is widely used to combat wear in such situations. D-gun coating is increasingly popular for such applications. Alumina-titania composite has been deposited on mild steel substrate. The coating has been characterized and their tribological responses have been evaluated. Resistance to erosion, evaluated through standard dry erosion test is highlighted in this work. An orthogonal full–factorial experimental matrix which includes all possible variables that contribute to brittle erosion was designed, conducted and validated. The variation of erosion rate with process parameters was mathematically modeled by using the regression analysis method.

Abstract: Gas shield electric arc coating of carbon steel surface is considered in relation to repair applications. Two types of wires are incorporated in the experiments including standard and nano-particle blended. The coating structure and the metallurgy are examined using the Scanning Electron Microscopy (SEM), and Energy Dispersive Spectroscopy (EDS). The microhardness of the resulting coating is measured and compared with the results obtained from the conventional wire. It is found that fine structures are formed in the coating due to the presence of nanoparticles. In this case, microhardness increases significantly in the coating.

Abstract: HVOF two layer coatings consisting of Diamalloy 2002 (top layer) and 4010 (bottom layer) onto carbon steel sheets are carried. The microstructure and chemical composition of the resulting coatings are examined using the Scanning Electron Microcopy (SEM) and Energy Dispersive Spectroscopy (EDS). The indentation tests are carried out to evaluate the microhardness and surface elastic modules of the resulting coatings. It is found that the coating produced for Diamalloy 2002 results in higher hardness and elastic modules than that corresponding to Diamalloy 4010.

Abstract: In this work, the results of studies on the preparation of carbon fibres (Tenax HTA40) for composites with an aluminium alloy matrix are presented. In the first step of preparation, the epoxy sizing was removed to assure adhesion of the Ni-P coating as a barrier to prevent the formation of brittle Al4C3. Removal of the sizing also decreases the risk of gas formation underneath the metal coatings in contact with the liquid metal matrix. Methods of sizing removal included annealing in air (300-600°C) and dissolving in solvents (acetone, toluene) and in inorganic solutions (HNO3, H2O2, NaOH), followed by SnCl2/PdCl2 activation are described. It was found that the chemical removal of epoxy sizing from carbon fibres is not an appropriate method for further studies on the electroless metallisation of carbon fibres. The thermal treatments in air atmosphere seem to be more useful for removing epoxy sizing. The result of the present studies was the optimisation of the temperature of the annealing of carbon fibres as 400-500oC. The morphology of the carbon fibre surface before and after sizing removal was characterised using SEM and in terms of the mass loss. A glycine-buffered electroless bath was used for the Ni-P coating of the fibre with a wide range of deposition rates and alloy compositions (2-12 wt% P). An advantage of electroless plating is that the process is carried out without electrical current. The coating is deposited as the result of the controlled reduction, which is catalysed by the metal being deposited. Two different pH values of metallisation baths were selected (pH=4.5 and pH=8.5). The time of Ni-P deposition ranged from 5 to 30 minutes. The process parameters were optimised for Ni-P coatings on 1D carbon fibres and 2D/3D woven fabrics. It was found that the process developed can be used for 2D and 3D woven fabrics.

Abstract: The carbon diffusion in steel, where the carbon diffusivity varies with the carbon content, was solved with the integral methods under the third boundary condition. The variation of carbon diffusivity in steel with the carbon content was described with two different functions, linear dependence and exponential dependence. The integral approximation for both cases was improved with the numerical computation to more accurately predict the carbon profiles. The integral solution is more accurate than the formulation based on the assumption of a constant diffusivity or those based on the assumption of a constant diffusivity and/or constant carbon content at part surface. It is also more easily used in practice than the numerical method to describe the carburising process and predict the carbon content at steel surface and carbon profiles in treated layer.

Abstract: This paper presents an investigation of the positive vacuum forming process. Previous research has indicated requirements of a draft angle of at least two to five degree and a depth to width ratio of not greater than 1:1. For specific formed geometry that required smaller draft angles and greater draw depths these limitations may make the positive vacuum forming process not applicable. The overall aim of this work was to allow the process to become more versatile. This work focused on three prototype moulds which were designed, manufactured, tested and analysed with a view to over come the present process limitations. Moulds were made of wood with a size of 68 x 68 x 75mm. Air holes of 1 and 10mm diameter were drilled in to these moulds in different positions. Polypropylene terephthalate glycol (PETG) materials was used to make the final product via the vacuum process. To release the product from the mould a constant 8bar pressure was applied. Proper time to make the final products and the quality of the final product were investigated. It was found that moulds with air holes opening in all surfaces resulted in shorter cycle times, lower air pressure and better quality of formed parts. It was also found in this work that a zero draft angle and as well as 1:1.1 draw depth was possible to achieve in the vacuum forming process.

Abstract: In recent years, it has been proposed that the new era of implants design should be focused on the use of the new generation of biocompatible materials or reengineers the currently available materials. The objective of this research was to study cell-metal interactions using highly porous TiO2 foam. To obtain the porous TiO2 foam, polymeric foam replication methods might be one of the most effective methods. Surface chemical composition, morphology and phase are investigated by field emission scanning electron microscope (FESEM) and X-Ray Diffraction (XRD). In vitro cellular response of cells has been studied on TiO2 foam. In the investigations of the cellular responses of cells, two aspects were considered: the number of growing cells and their morphological features. It was clear that rough surface morphology was important factor for better cell-metal interaction. Surface topography can affect the cell migratory significantly and adhesion behavior on implant surfaces.

Abstract: Black powders coming from the interactions of pipe and other metals with the environment in gas transmission line can cause severe problems in the industry. In this work the composition of the collected black powder from up stream of the filtering system analyzed using XRF and XRD techniques. Erosion test is carried on the samples of impeller alloy in the black powder alcoholic slurry in a laboratory set up. It is shown that the main constituent of the black powder is magnetite. The rotation speed and presence of humidity can enhance the erosion/corrosion with the consequence of more black powder production.

Abstract: Pulse electrodeposition was used to produce nanocrystalline (nc) copper from copper sulfate electrolyte with saccharin as additive. The grain size of nanocrystalline coatings was determined using x-ray diffraction and atomic force microscopy (AFM) which was about 30 nm. Microcrystalline copper deposits were also produced by direct current electrodeposition processes and compared with pulse plated ones. Corrosion behavior of the coatings was investigated using polarization and Impedance measurements in different solutions. The oxidation test was carried out at 650°C in an electrical furnace. It was demonstrated that the nanocrystalline film was markedly superior to regularly grained films made by direct current (DC) plating; nanocrystalline deposits show higher corrosion resistance and much higher oxidation resistance.

Abstract: The present work deals with a new method, technology and equipment developed for “in depth surface hardening” of large rotary details and tools, made of constructional, carbon, alloyed or low-alloyed tool steels. According to the technical requirements the details and tools have to possess hardened layer with specific shape, depth in the range 20-35mm and surface hardness of 35-62 HRC. The “in-depth hardening” was performed by quenching and self-tempering. Preliminary volume heating and depth regulated local surface adjustable gas-flame heating were used. The gasflame heating was realized by gas-flame burners (CH4+O2) located near the details’ periphery, depending on the shape and depth of the hardened layer. The burners’ power and heating time were adjustable. The cooling was performed by showers located near the details’ periphery also depending on the shape of the hardened layer. Water or polymer water solution was used as cooling media and its capacity was adjusted in the beginning. Due to the heat accumulated during the preliminary heating and the heating up to the quenching temperature of the surface layer, after stopping the cooling, subsequent self-tempering was applied. All of the equipment for realizing the whole hardening cycle, temperature and time control and parameters of heating and cooling was developed. Series of different details were hardened: traversing wheels and gears, forming rolls, rolling disks etc., made of construction and tool steels. The hardened layers obtained were with specific shape, surface hardness in the range of 35-60HRC and depth of the hardened layer of 15- 25mm.