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Proceedings Papers
ITSC2023, Thermal Spray 2023: Proceedings from the International Thermal Spray Conference, 258-265, May 22–25, 2023,
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Cold spraying has great potential for additive manufacturing, especially of oxidation-sensitive metals, because the material is not melted and significantly higher deposition rates can be achieved than with conventional additive manufacturing processes such as selective laser melting or direct metal deposition. Titanium is regarded as a high-performance engineering material due to its unique combination of properties, including good corrosion resistance, biocompatibility and high strength at comparatively low density. However, due to its high price, it appears reasonable for many applications to use material compounds in which titanium is only used on the surface of the workpiece, while less expensive materials such as aluminum are used for the remaining volume. In the present work, cold sprayed pure titanium coatings were deposited on Al substrates and then formed to defined 3-dimensional final contours by die forging and rotary swaging. Different porosities were selectively set in order to evaluate their influence on the coating adhesion and cohesion in the forming process. Pre-consolidation of the coatings and the use of Al/Ti interlayers proved to be promising strategies.
Proceedings Papers
ITSC 2021, Thermal Spray 2021: Proceedings from the International Thermal Spray Conference, 247-255, May 24–28, 2021,
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In this study, a novel strategy to manufacture high strength cold-sprayed Al coating by using powder with wide size distribution is proposed. The microstructure and mechanical properties of deposited coating sprayed at three typical impact velocities before and after heat treatment are investigated. Furthermore, the deposition and strengthening mechanisms of the coating sprayed at various impact velocities are clarified. The results show that the coating with higher density and mechanical properties can be successfully fabricated by cold spray at comparatively low particle impact velocity. The mechanical properties were enhanced with the contribution of heat treatment process. It is the in-process tamping effect induced by larger powder that results in the severe plastic deformation thus leads to densification and excellent mechanical properties of the cold-sprayed Al coating.
Proceedings Papers
ITSC 2021, Thermal Spray 2021: Proceedings from the International Thermal Spray Conference, 508-514, May 24–28, 2021,
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Thermally sprayed WC-Co coatings provide excellent wear resistance and corrosion protection under heavy loads, but their application usually involves additional grinding and polishing steps, which can be 3-4 times costlier than the spraying process itself. There is thus the motivation to develop a process that produces smooth, near-net-shape carbide coatings. This contribution is an investigation of WC-12Co coatings obtained by suspension HVOF spraying. Significant work was devoted to the development and characterization of water-based hardmetal suspensions synthesized from commercially available WC and Co powders. The suspensions produced were sprayed using the HVOF process, and the resulting coatings were evaluated based on microstructure, hardness, and phase composition.
Proceedings Papers
ITSC 2019, Thermal Spray 2019: Proceedings from the International Thermal Spray Conference, 119-124, May 26–29, 2019,
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The present work demonstrates the possibilities of atmospheric air plasma spraying. It presents various approaches to the development and optimization of spraying modes using diagnostic equipment and provides examples of industrial approbation of the technology.
Proceedings Papers
ITSC 2019, Thermal Spray 2019: Proceedings from the International Thermal Spray Conference, 789-794, May 26–29, 2019,
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This study employs a three-dimensional simulation to investigate the cold gas dynamic manufacturing process. During the buildup of the desired object, sharp edges, stagnation points, and corners are likely to form that can influence the trajectories of the particles. This leads to dispersion and lack of particle deposition in these areas, which can eventually reduce the precision and efficiency of the build process. A cylindrical and frustum-shaped object are numerically simulated on a substrate to represent typical additively manufactured parts. Particle trajectories and impact conditions with and without these objects are compared. The results provide useful information for understanding the limitations and challenges associated with cold gas dynamic manufacturing, which can help improve the quality and precision of the process.
Proceedings Papers
High Deposition Efficiency Additive Manufacturing of Titanium Using Low Pressure Nitrogen Cold Spray
ITSC2016, Thermal Spray 2016: Proceedings from the International Thermal Spray Conference, 12-17, May 10–12, 2016,
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In this work, fully dense titanium parts are fabricated by cold gas dynamic spraying (CGDS). Titanium powder is deposited using a low-pressure CGDS process with nitrogen as the carrier gas. The density, porosity, hardness, and tensile properties of the parts produced are determined and discussed.
Proceedings Papers
ITSC 2010, Thermal Spray 2010: Proceedings from the International Thermal Spray Conference, 345-351, May 3–5, 2010,
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An experimental set-up has been developed, at the SPCTS Laboratory, to produce fully melted, millimeter-sized, ceramic or metallic drops with impact velocities up to 10 m/s. Such impact velocities allow reaching impact Weber numbers, close to those of the plasma spray process (We = 2300). A fast camera (4000 image/s) combined to a fast pyrometer (4000 Hz), allows following the drop flattening. For studding the flattening at the micrometer scale, a DC plasma torch is used to melt micrometer sized alumina particles (around 45 μm). The experimental set-up is composed of a fast (50 ns) two-color pyrometer and two fast CCD cameras (one orthogonal and other tangential to the substrate). The flattening of millimeter and micrometer sized particles is compared. First are studied impacts of alumina drops (millimeter sized) with impact velocities up to 10 m/s. Then are considered micrometer sized alumina particles (about 45 μm in diameter) sprayed with a DC plasma torch. A correlation has been found between both flattening scales and, in spite of the lower impact velocity at the millimeter scale, ejections are also found at the micrometer scales. This work shows that to compare phenomena at the two different scales it is mandatory to have Weber numbers as close as possible in both cases.
Proceedings Papers
ITSC 2009, Thermal Spray 2009: Proceedings from the International Thermal Spray Conference, 308-313, May 4–7, 2009,
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This presentation reviews the features and capabilities of the KM-Coating Development System, a tool that provides hands-on experience with the kinetic metallization process. The latest version of the tool incorporates mass flow controllers that facilitate gas mixing and computerized feeding of ultra-fine and highly agglomerating powders. Coatings and spray-formed products produced with the new system are presented along with corresponding material properties.
Proceedings Papers
ITSC 2009, Thermal Spray 2009: Proceedings from the International Thermal Spray Conference, 883-888, May 4–7, 2009,
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The aim of this work is to investigate the effect of substrate surface chemistry (e.g., oxidation and atom diffusion) on the flattening of a single millimeter-sized alumina drop. To that end, a new technique to produce such drops with different impact velocities has been developed. It consists of a rotating crucible heated by a transferred plasma arc and a piston that controls substrate velocity and, as a result, the impact velocity of the drop. A fast camera working in concert with a fast pyrometer precisely records drop flattening and cooling. This system makes it possible to study interface phenomena, such as desorption and wettability, as well as the effects, at impact, of the kinetic energy or Weber number of the flattening drop.
Proceedings Papers
ITSC 2007, Thermal Spray 2007: Proceedings from the International Thermal Spray Conference, 770-775, May 14–16, 2007,
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A variety of metallic powder particles were thermally sprayed onto the mirror polished metallic substrate surface and the effect of both substrate temperature and ambient pressure on the flattening behavior of the particle was systematically investigated. In the flattening behavior of the sprayed particle onto the substrate surface, critical conditions were recognized both in the substrate temperature and ambient pressure. That is, the flattening behavior changed transitionally on that critical temperature and pressure range, respectively. A transition temperature, Tt, and transition pressure, Pt, were defined and introduced, respectively for those critical conditions. The fact that the dependence both of transition temperature and transition pressure on the sprayed particle material had similar tendency indicated that the wetting of the substrate by the molten particles seemed to be domination in the flattening. Three dimensional transition curvature by combining both transition temperature and transition pressure dependence was proposed as a practical and effective controlling principle of the thermal spray process.
Proceedings Papers
ITSC 2007, Thermal Spray 2007: Proceedings from the International Thermal Spray Conference, 230-235, May 14–16, 2007,
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Three-dimensional molecular dynamics simulation was conducted to clarify at an atomic level the flattening process of a high-temperature droplet impacting a substrate at high speed. The droplet and the substrate were assumed to consist of pure aluminum, and the Morse potential was postulated between a pair of aluminum atoms. In this report, the influences of the impact parameters, such as the droplet velocity and the droplet diameter on its flattening behavior were analyzed. As a result, following representative conclusions were obtained: (1) the flattening ratio increases in proportion to the droplet velocity and the droplet diameter; (2) the flattening ratio for nanosized droplet can be rearranged by the same dimensionless parameters of the proper physical properties, such as the viscosity and the surface tension, as those used in the macroscopic flattening process.
Proceedings Papers
ITSC 2007, Thermal Spray 2007: Proceedings from the International Thermal Spray Conference, 365-370, May 14–16, 2007,
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The effect of nano and microstructured powders in cored wires on formation and properties of Fe-TiB 2 composite coatings by high velocity arc spraying (HVAS) was investigated. Six cored wires filled with different average ceramic particle sizes (20-40 nm, 2 µm, and 420 µm) and fine powder contents (0, 8, 16, 20, 24, 32wt.%) were sprayed. The flattening behavior of sprayed particles was characterized and compared by using optical microscopy (OM) and 3D Surface Profiler. The microstructure of the coatings and phase compositions were characterized by means of Laser Confocal Scan Microscopy, SEM, EDAX and XRD. Hardness and wear properties were evaluated. The results showed that the splat shape of the cermets has a transitional tendency to change from a distorted heavy splash to a disk with little splash with (i) increasing the percentage of fine ceramic particles and (ii) decreasing coatings porosity. Fe –2 µm 32% TiB 2 coatings reveals a dispersion of fine ceramic particles and less scattering of hardness, which improved the wear resistance and changed the abrasion mode.
Proceedings Papers
ITSC 2005, Thermal Spray 2005: Proceedings from the International Thermal Spray Conference, 100-105, May 2–4, 2005,
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Especially, composites of aluminium metal foams are of high potential for lightweight applications in automotive, aerospace and general engineering because of their excellent ratio of low weight and high stiffness. To fulfill the industrial need for these new materials as soon as possible, a new integrated manufacturing process concept has been developed and studied at our institute. The new “easyFoam-process” concept consists of four basic steps: production of semi-finished parts via the powder metallurgical route, forming of the foamable semi-finished part into a near net shape by extrusion or any standard aluminium-forming process, coating of the surface by thermal spraying and foaming by inductive heating. Thus it’s feasible to provide a fast, continuous and efficient production of metal foam composites with highly reproducible properties, resulting in eminent advantages over current techniques for foam sandwich production in terms of degree of anisotropy, statistical spread in foam properties and production economy. This process is also the only one being able to produce a graded pore structure in symmetrical parts of PM-aluminium foams. The thermally sprayed coatings serve simultaneously as mould and as future multifunctional coating. In this paper, some results of our first study in coating the foamable Al-tubes and inductive heating the coated parts are presented.
Proceedings Papers
ITSC 2005, Thermal Spray 2005: Proceedings from the International Thermal Spray Conference, 199-207, May 2–4, 2005,
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Development of new, low-cost methods for spraying near net shapes of Titanium and Titanium alloys is critical for many industries and applications. Direct fabrication technologies would have an impact on many industries because of the potential to quickly manufacture complex parts or additive features with minimal waste. However, currently used high temperature spray technologies (Lasform, thermal spray methods) involve melting and solidification. Each new layer starts out molten, then solidifies, and must eventually cool to room temperature. This report presents results of feasibility tests for development of a new method of direct fabrication of Ti alloy parts at near-net shapes (nns) using the Cold Spray process (CSP). Several Ti-6Al-4V powders including gas atomized, plasma atomized, and hydride dehydride were tested in these experiments. Feedstock powders were characterized for particle size distribution, morphology, chemical composition, hardness, and deposition efficiency. Coatings in thicknesses of 2 mm were sprayed for evaluation of microstructure, hardness, and porosity. Thick rectangular prisms (10 mm) were sprayed for machining tensile specimens. The material properties of as sprayed and post treated coatings by heat-treating and hot isostatic pressing (HIPing) on material properties was studied. Analysis showed that after HIPing the density of sprayed Ti-6Al-4V coupons is near 100% and material properties met or exceed those of wrought material.
Proceedings Papers
ITSC 2005, Thermal Spray 2005: Proceedings from the International Thermal Spray Conference, 251-253, May 2–4, 2005,
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Cold spray, a new member of the thermal spray process family, can be used to prepare dense, thick metal coatings. It has tremendous potential as a spray forming process. However, it is well known that significant cold work occurs during the cold spray deposition process. This cold work results in hard coatings but relatively brittle bulk deposits. We have investigated the mechanical properties of cold sprayed aluminum and the effect of annealing on those properties. Cold spray coatings approximately one centimeter thick were prepared using three different feedstock powders: Valimet H-10, Valimet H-20, and Broadman Flomaster. ASTM E8 tensile specimens were machined from these coatings and tested using standard tensile testing procedures. Each material was tested in two conditions: as-sprayed and after a 300°C, 22 h air anneal. The as-sprayed material showed high ultimate strength and low ductility, < 1% elongation. The annealed samples showed a reduction in ultimate strength but a dramatic increase in ductility, up to 10% elongation. The annealed samples exhibited mechanical properties similar to wrought 1100 H14 aluminum. Microstructural examination and fractography clearly showed a change in fracture mechanism between the as-sprayed and annealed material. These results indicate good potential for cold spray as a bulk forming process.
Proceedings Papers
ITSC 2005, Thermal Spray 2005: Proceedings from the International Thermal Spray Conference, 311-319, May 2–4, 2005,
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Copper splats are deposited on the flat stainless steel surface at the ambient and preheated conditions. The splashing occurs as the splats are deposited at an ambient atmosphere. The characteristics of the splashing occurring at different splat regions during spreading of the droplet are examined. The splashing can be classified into two types according to the splashing mechanisms. At the surrounding region of the splat larger than flattening ratio about 1.5 to 2, the radial splashing takes place by jetting-away of splat materials, which leads to the formation of a splat with a reduced diameter. At the central area of the reduced splat, the upward splashing occurs through the blowing up of the top surface layer which results from the high pressure of gas bubbles. At the preheated condition which can remove surface adsorbates, no evident splashing occurs under the normal spray conditions. Two types of splashing can be explained by the gases evolved through evaporation of the adsorbates resulting from the heating of the high temperature droplet. The spreading of the droplet involved in the wave urging flow is presented.
Proceedings Papers
ITSC 2005, Thermal Spray 2005: Proceedings from the International Thermal Spray Conference, 460-464, May 2–4, 2005,
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The electromagnetic forming (EMF) is a process for forming sheet metals or thin metal tubes with a high electrical conductivity such as Al-alloys. Extremely high forming velocities can be achieved by employing this process based on pulsed electro-magnetic fields. To exploit the advantages of this process in forming sheet materials with a limited electrical conductivity thermal spraying methods have been applied. The essential requirement is based on the design and development of an electrically conductive layer system, which can act as a “driver“ for materials to be formed. Therefore, the layer has to fulfil high demands on its density as well as on the adhesion to the substrate. In this contribution a new coating concept for thin sheets to be electromagnetically formed is presented. The influences of pre-cleaning processes, coating parameters, layer properties and sheet thickness on the deformation are scrutinized. Accompanying metallographic, mechanical and microscopic investigations of the coated layers help to understand the mechanisms of materials behaviour during EMF processes.
Proceedings Papers
ITSC 2005, Thermal Spray 2005: Proceedings from the International Thermal Spray Conference, 579, May 2–4, 2005,
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It is known that particles injected in a plasma stream follow differing trajectories which in turn leads to different thermal and kinetic history dependent on the location of particle in the plume. The variation in particle characteristics (temperature and velocity) across the plume has been the focus of research over the years. The corresponding variation in impacting particles, particularly in terms of their splat characteristics have not been explored as systematically. This is important for a complete understanding of the coating build-up phenomena and the variations in coating properties. This paper presents the results of a study in which the spatial variation in particle properties is mapped to the spatial variation in splat properties. This has been accomplished using a procedure to collect splats using a shutter mechanism that allows us to expose the substrate for approximately 50 milliseconds. Splats of Alumina and a Ni- Cr-B-Si-Mo have been collected on polished substrates maintained at 250ºC and studied. Micrographs reveal differing splat morphologies across the spray plume – from missing-cores in one part to complete disc-shaped splats in the other. Extent of flattening and fragmentation have been quantified and found to vary within the ‘splat map’. Correlation between the location of particle in the plume and the resulting splat has been constructed using this data. Abstract only; no full-text paper available.
Proceedings Papers
ITSC 2003, Thermal Spray 2003: Proceedings from the International Thermal Spray Conference, 863-869, May 5–8, 2003,
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The particle parameters including particle size, velocity and temperature influence significantly splat formation process in thermal spraying. The flattening degree of subsequent splat determines the coating structure and properties. Both theoretical analysis and simulation of splatting process indicate that the flattening degree depends on Reynolds number (Re) of spray particles. The experimental correlations suggest that the theoretical models overestimate the flattening degree. In the present study, with careful control of particle size and measurement of particle velocity and temperature, the relationship between the flattening degree and particle Reynolds number is examined experimentally. Copper powders of small size range are used to ensure valid of mean particle size. Plasma spraying is carried out under different conditions to change particle velocity and temperature. The particle velocity and temperature are measured using DPV- 2000. Splats were deposited on preheated polished stainless substrate surface. The diameter of individual splat was measured. The flattening degree was estimated using average diameter of splats and spray particles for individual spray condition. Using the exponential formula of Re with a power of 0.2, it was found that experimental correlation yielded a coefficient about half of that given by Madjeski’s model.
Proceedings Papers
ITSC 2003, Thermal Spray 2003: Proceedings from the International Thermal Spray Conference, 875-882, May 5–8, 2003,
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A thermal spray coating is formed through successive impact, flattening, rapid cooling and solidification processes of a stream of spray droplets. Splashing may occur during droplet flattening process. Recent studies suggested that splashing can be suppressed when a molten droplet impacts on a preheated flat substrate. In this study, the splatting behavior in plasma spray is examined using molten spray droplets of different Reynolds number. Splats are deposited on preheated flat stainless steel surface. The morphology of splats is examined using optical microscopy and scanning electron microscopy. To adjust Reynolds number of spray droplets, copper droplets are produced using both Ar-H 2 and Ar-He-H 2 plasma jets under different operating conditions. As a result, the Reynolds number of spray droplets have been varied from about 18,000 to 90,000. It has been found that Reynolds number will influence splashing phenomena during splatting and consequent splat morphology. At low Reynolds number, splats present a regular disc morphology. However, when Reynolds number was increased up to about 5x104, the severe splashing around periphery of splat droplet was clearly observed despite the preheating of substrate. Based on the morphology of splats, a model for the spreading of molten droplet is proposed to explain the effect of Reynolds number on the flattening behavior of molten spray droplet.
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