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.

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.

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.

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.

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.

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.

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.

This paper presents a process for manufacturing parts using HVOF spraying techniques. The parts are made from a mixture of chromium carbide and nickel chromium alloy powders and are characterized based on microstructure, hardness, and corrosion and wear performance. Paper includes a German-language abstract.

This work investigates the use of thermal spray molding in the production of microscale components with large aspect ratios. It evaluates a number of spraying processes and coating materials and discusses the impact of the base material on process control and product properties. It also demonstrates the use of simulation for determining optimal process conditions. Paper includes a German-language abstract.

Titanium aluminide shows good potential for lightweight applications at high temperatures, provided various problems are overcome. The primary problem, low-temperature brittleness, can be resolved through a combination of laser cladding and directional solidification. This paper explains how Ti48Al2Cr alloy is applied and how process parameters must be chosen so that directional solidification occurs. This involves the use of FEM simulations, carried out in parallel with experimental work, to determine temperature gradients and cooling rates at the solidification front and in the melt pool and their effect on solidification structures. Paper text in German.

Reusable space vehicles, which must withstand re-entry into the Earth's atmosphere, require external protection systems (TPS) which are usually in the forms of rigid surface in areas of high or moderate working temperature. High heat fluxes and temperatures related to high performance hypervelocity flights also require the use of TPS materials having good oxidation and thermal shock resistance, dimensional stability, and ablation resistance. Components by these materials are usually fabricated, starting from either billets or plate stocks, by uniaxial hot pressing, and complex parts, such as low radius edges, are then obtained by electrical discharge machining technique. This article investigates an alternative fabrication technology, based on plasma spraying, to produce near net shape components. Results of experimental activities, such as optimization of plasma spraying parameters based on a DOE approach, are reported and discussed.

The growing need for new materials and material combinations with superior properties for severe service applications has led to the development of near net-shape forming techniques for certain materials, such as superalloys, refractory metals (Ta, W, and Mo) and highly reactive metals (Ti and its alloys). Vacuum plasma spray (VPS) was used to produce dense Ti-6Al-4V deposits for mechanical properties evaluation. Spherical Ti-6Al-4V powder, produced by Plasma Atomization (PA), a novel patented powder fabrication technique, was used as the starting powder. Plasma atomized Ti-6Al-4V powder characteristics include: high purity, tight particle size range, highly spherical with no attached satellites, and excellent flowability. The resulting as-sprayed Ti-6Al-4V deposits were dense and low in oxygen content. Thermal treatment was conducted after spraying in order to improve the structure and the properties of the spray formed material. The mechanical properties of the material, including tensile strength, elongation and hardness, in both the as-sprayed and the heat treated conditions were compared. The mechanical properties of these preliminary VPS Ti-6Al-4V specimens indicate that the combination of high purity starting powder and controlled environment deposition can be used to produce dense spray formed Ti-6Al-4V structures with properties comparable to those of cast or sintered powder metallurgy parts.

Near net shape spray forming technologies have matured into viable manufacturing techniques. Spray forming can be accomplished with many different thermal spray technologies yielding a range of materials with different properties. Monolithic materials, composite materials, and multi-layer materials have all been made. Mechanical properties comparable to cast versions of the parent material are achievable for some materials and processes. Tailored properties can also be achieved for such characteristics as high hermeticity, thermal protection, electrical isolation, wear resistance, etc. A review of materials and properties is presented.

Alumina matrix composites reinforced with metal thin wire (Inconel-600) were successfully fabricated by plasma spray forming. The atmospheric plasma sprayed matrix layers and wire layers arranged by filament-winding technique were piled up alternately. Though the matrix and the wire were partially bonded only on the side which sprayed particles came flying to, a solid structure was obtained by this technique. Spraying in one direction perpendicular to the substrate made peculiar V-shape pores around the wires, but tilting the torch was effective to reduce the pores. The flexural strength of composite did not increase in spite of some crack deflections on the fracture surface. Owing to the wire pullout, however, the composite exhibited a remarkably higher apparent fracture energy than that of monolithic alumina ceramics.

Thermoelectric (TE) power generation from waste heat is recently attracted much attention as one of energy-saving technologies. In this paper, Co-doped n-type iron silicide semiconductor was plasma sprayed under various spray conditions to find the optimum spray-forming conditions. Then Co-doped iron silicide TE device with thickness ranging from 3 to 5 mm and the area of over 100 cm square was produced in the form of a plate or on tube. The paper examines the microstructure and evaluates thermal and electric properties. Paper includes a German-language abstract.

The feasibility of using the HVOF process for the thermal spray-forming of free-standing components has been investigated. HVOF spray forming offers a number of potential advantages compared to the established procedure of plasma forming, including increases in component density, and reduction in material decomposition during spraying. Using blends of carbide and superalloy powders in various proportions, HVOF spraying has been successfully used to form free-standing cylinders and cones of various lengths and thicknesses. Microstructural examination of the spray-formed material, using optical microscopy and scanning electron microscopy (SEM), has shown a homogeneous distribution of carbides in the superalloy matrix, with very low levels of porosity. Vickers microhardness has been measured on several sprayed forms. In order to complete the study of the different systems, abrasion (Rubber Wheel Test), friction (Ball on Disk Test) and erosion wear results have been obtained. These wear results have been used in order to evaluate the behaviour of the sprayed samples with a different powder percentage in the blends. Corrosion tests have been done to evaluate the corrosion resistance of the sprayed samples (ASTM D-1411).

In this study, ethylene methacrylic acid copolymer (EMAA) was used as the matrix to produce EMAA/Al2O3 and EMAA/NiCr composite coatings from dry-blended powder mixtures. This work was conducted to determine processing concerns when using similar sized reinforcement particles of different density in a flame-spray process. This work has utility for applications that require a reduction in mechanical wear and/or to confer upon a polymeric deposit a certain functional property by the introduction of value-added powder. Free-standing coatings were produced to test the mechanical properties of the sprayed deposit. The effects of the filler content on the secant modulus, yield stress, and tensile strength are discussed. The differences in deposition efficiencies among the EMAA, Al2O3, and NiCr are highlighted with respect to particle size and density.

Directed light fabrication (DLF) is a rapid fabrication process that fuses gas delivered metal powders within a focal zone of a laser beam to produce fully dense, near-net shape, 3D metal components from a computer generated solid model. Computer controls dictate the metal deposition pathways, and no preforms or molds are required to generate complex sample geometries with accurate and precise tolerances. The DLF technique offers unique advantages over conventional thermomechanical processes or thermal spray processes in that many labor and equipment intensive steps can be avoided to produce components with fully dense microstructures. Moreover, owing to the flexibility in power distributions of lasers, a variety of materials have been processed, ranging from aluminum alloys to tungsten, and including intermetallics such as M05Si3. Since DLF processing offers unique capabilities and advantages for the rapid fabrication of complex metal components, an examination of the microstructural development hhas been performed in order to define and optimize the processed materials. Solidification studies of DLF processing have demonstrated that a continuous liquid/solid interface is maintained while achieving high constant cooling rates that can be varied between 10 to 10 5 Ks-1 and solidification growth rates ranging up to 10-2 ms-1.

Future X-ray space missions will require telescopes with very large effective area, good angular resolution and low weight. To obtain these characteristics it is necessary to produce very thin and light mirror shells that, once integrated into a suitable mechanical structure, will fulfil the requested specifications. To meet these requirements, one approach which seems promising is the use of ceramic materials combined with the plasma forming technology to produce ceramic carriers that are subsequently used to manufacture the x-ray mirror shells by means of the epoxy replication technology on superpolished mandrels. The CEA/Le Ripault has shown the feasibility of producing ceramic carriers (diameter: 600 mm, height: 239 mm). The mass saving is substantial in comparison with the nickel electroforming technology which is now used to manufacture high throughput, medium angular resolution x-ray optics. The achieved out of roundness of the carriers is ± 70 microns; an effort must still be made to meet the requested specification of ± 20 microns.

Plasma spraying, commonly used for wear and heat resistant barriers, can be used to produce free-standing bulk ceramic parts as well. In this work the microstructure and phase development of a bulk plasma-sprayed alumina material with about 14 % porosity and splat like grains is investigated in the as-sprayed and various annealed material conditions, using electron microscopic and x-ray diffraction techniques. The fracture characteristics are investigated using standard CT specimens in in-situ SEM experiments. The mechanical response of the material is clearly a result of two features: the pronounced alignment of microstructure itself, and the occurrence of a splat-internal microcrack sub-structure in the as-sprayed condition. This microcrack substructure is a consequence of a splat internal columnar subgrain structure which occurs as a result of the rapid cooling conditions on deposition. The morphology of this subgrain structure and its phase composition is seen to change extensively on annealing. It is found that the mechanical behaviour of the as sprayed material is dominated by this internal subgrain structure, but the behaviour of sufficiently annealed material is dominated by the morphology and mechanical stability of the splat like grains themselves. The biggest change on annealing is not an overall sintering effect, but rather the recrystallisation of the splat internal substructure