There is a continued need within the aerospace and space communities to increase the structural efficiency of launch vehicles in order to increase the payload and/or lower fuel usage. Many of these structures have critical stiffness demands because of deflection, buckling, or acoustic/vibration damping. Aluminum-beryllium (Al-Be) is a candidate material for many such structural components because it has a very high stiffness to weight ratio (second only to pure beryllium) and has superior formability and weldability as compared to beryllium. The strength to weight ratio of commercial Al-Be is superior to aluminum alloys (7050 and 6061-T6) that are currently used for aerospace and space applications. Plasma spray forming of Al-Be alloys is being investigated at Los Alamos National Laboratory for producing axial symmetric components for aerospace and space applications. Plasma spray forming of beryllium and beryllium alloys was investigated during the 1960's and 70's by Union Carbide Speedway Laboratories and the Atomic Weapons Establishment for producing axial symmetric launch vehicle components for defense related applications. Information is presented on the thermal and mechanical properties of plasma sprayed AlBeMet which is a commercial Al-Be alloy produced by Brush Wellman Inc.

Plasma spraying is under investigation as a method for in-situ repair of damaged beryllium and tungsten plasma facing surfaces for the International Thermonuclear Experimental Reactor (ITER), the next generation magnetic fusion energy device, and is also being considered as a potential fabrication method for beryllium and tungsten plasma-facing components for the first wall of ITER. Investigators at the Los Alamos National Laboratory's Beryllium Atomization and Thermal Spray Facility have concentrated on investigating the structure property relationship between the as-deposited microstructures of plasma sprayed beryllium coatings and the resulting thermal properties of the coatings. In this study, the effect of the initial substrate temperature on the resulting thermal diffusivity of the beryllium coatings and the thermal diffusivity at the coating/beryllium substrate interface (i.e. interface thermal resistance) was investigated. Results have shown that initial beryllium substrate temperatures greater than 600°C can improve the thermal diffusivity of the beryllium coatings and minimize any thermal resistance at the interface between the beryllium coating and beryllium substrate.

The exceptional properties of beryllium (Be) including low density and high elastic modulus, make it the material of choice in many defense and aerospace applications. However, health hazards associated with Be material handling limit the applications that are suited for its use. Innovative solutions that enable continued use of Be in critical applications while addressing worker health concerns are highly desirable. Plasma Transferred Arc solid freeform fabrication is being evaluated as a Be fabrication technique for civilian and military space based components. Initial experiments producing beryllium deposits are reported here. Deposit shape, microstructure and mechanical properties are reported.

The development of beryllium first wall components for future magnetic confinement fusion experiments such as the International Thermonuclear Experimental Reactor (ITER) is a topic of great importance as the ITER construction phase is about to begin. The beryllium components must be able to survive the harsh plasma environment for extended periods of time during operation. Furthermore, cost and detrimental health effects must be kept to a minimum during the fabrication and operation processes. The work described here details the requirements for ITER first wall components and describes experiments to produce beryllium high heat flux components by plasma spray deposition. Experimental parameters and characterization results from the components are presented. Results of initial high heat flux testing under electron beam irradiation show performance exceeding that required for ITER first wall components.

During the last decades, the application of copper alloys has become very prominent in engineering. Judging from the properties of bulk materials or galvanic copper coatings, a thermal sprayed coating shows significant disadvantages. The reason for this effect is the build up of a thermal sprayed coating by individual droplets. The main aim of this work is to improve the properties of the twin wire arc sprayed copper alloys, thereby expanding the application of these kind of coatings to the areas where galvanic copper plating technique are mainly used. A copper-cobalt-beryllium alloy has been investigated and the possibility of its application in the twin wire arc process evaluated. The arc sprayed coatings were classified based on the properties of bulk material. The improvement of properties like hardness is based on an investigation of several spraying parameters of the arc spray process. To achieve a maximum value of thermal or electrical conductivity, minimum porosity of the coatings was the aim. Furthermore, a post heat treatment of the sprayed coatings, with the aim of reducing residual tensile stresses within the coating and to improve the wear resistance by means of hardening effects, was carried out. The investigations involved metallographic examination of the coatings using optical microscopy and scanning electron microscopy. Phase composition and residual stresses were detected by X-ray diffraction analysis. Microhardness was measured in the as sprayed as well as in the heat treated state.

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.

This paper describes the development and evaluation of multifunctional coatings for outdoor parabolic antennas. The plasma-sprayed composite coatings provide corrosion protection, reduce solar heating, and improve the absorption of EM radiation at the edges of the antenna while impeding its flow in other areas. The coatings also reduce the impact of the support structure on antenna performance. Paper includes a German-language abstract.

Plasma sprayed tungsten coatings are considered as potential candidates for materials in contact with the plasma in future fusion reactors. In this work, the thermal shock resistance of these coatings is studied to determine which of five changed deposition parameters most influences the coating's performance. The thermal shocks were generated with a pulsed electron beam gun. The pulse duration was 0.2 and 0.5 s and the absorbed power density 60 MW/m 2 . Two series of samples were analyzed. One was plasma sprayed at atmospheric pressure (AP) and the other at low pressure (LP). The LP coatings were deposited on a molybdenum alloy (TZM). AP coatings were deposited on molybdenum and on water cooled copper coupons for fatigue tests. The porosity seems to be a positive factor for thermal shock resistance. The thickness of the coatings and the spraying atmosphere were found to strongly influence the thermal shock resistance. In the case of the fatigue test, some coatings withstood up to 1000 shocks of 0.5 s duration.

With the vast array of coating technologies and materials available in the marketplace, matching the best coating to an application is far from a trivial task. There is a tendency on the part of vendors, for example, to put forward any hard coating as a chrome replacement or any corrosion-resistant coating as an alternative to cadmium. At the same time users often attempt to shoehorn the coatings with which they are most familiar into applications for which they are not well-suited. This paper will discuss how best to match the application to the best technology and material, considering all the critical requirements of fit, form and function, with particular reference to alternatives for chrome and cadmium plating.

Zirconium metal coatings applied by plasma spraying and electrospark deposition (ESD) have been investigated for use as diffusion barrier coatings on low enrichment uranium fuel for research nuclear reactors. The coatings have been applied to both stainless steel as a surrogate and to simulated nuclear fuel uranium-molybdenum alloy substrates. Deposition parameter development accompanied by coating characterization has been performed. The structure of the plasma sprayed coating was shown to vary with transferred arc current during deposition. The structure of ESD coatings was shown to vary with the capacitance of the deposition equipment.

Wear resistant thermal spray coatings are hard but brittle, making them useless for applications sensitive to metal fatigue. New coatings have been developed, however, that resist crack formation under load as well corrosion and wear. This study compares the properties and behaviors of many of these coatings along with chrome plating using standard test methods.

Plasma-sprayed ceramic coatings exhibit a lamellar structure with a mean bonding ratio of less than 32%, which dominates coating properties and limits the performance that can be achieved. In this study, yttria-stabilized zirconia (YSZ) coatings were plasma sprayed at different deposition (substrate surface) temperatures up to a maximum of 1100 °C. The lamellar mean bonding ratio, estimated from the ionic conductivity of the YSZ coatings, was found to increase from 32% in room temperature deposits to more than 75% in the deposits prepared at 1100 °C. Evidence of this improvement is also observed in fractured deposit cross-sections. The results show that controlling deposition temperature is an effective way to optimize lamellar interface bonding and, as a result, coating properties.

Thermal spray coatings are very effective in combating wear and corrosion in many applications. New thermal spray processes and coating compositions continue to be developed with concomitant improvements in the performance of the coatings and their use in new applications. Nonetheless, the thermal spray coatings are not without competition from other coating and overlay processes and materials. This brief review considers the microstructures and the wear and corrosion resistance of a number of alternative coatings to thermal spray coatings, including physical vapor deposition, chemical vapor deposition, electroplating, autocatalytic, and laser cladding.

This study demonstrates the use of bulge testing to evaluate fuel plates for high-performance nuclear reactors. Uranium-molybdenum alloy substrates were plasma sprayed with zirconium and clad between aluminum sheets by hot isostatic pressing. The coated-and-clad samples were cut into disks, the top cladding was thinned, and a small hole was milled through the bottom cladding. The samples were then placed in a pressure cell and a syringe pump was used to inject distilled water through the hole in the bottom Al sheet. Two cameras measured bulge height while fluid pressure was simultaneously recorded. Test results show that all failures occurred at the plasma-sprayed Zr/U-Mo interface rather than the HIP-bonded Zr/Al interface. It is also shown that the use of transferred arc (TA) cleaning prior to spraying improves both failure pressure and initiation fracture toughness, especially under high ac current. TA cleaning facilitates the formation of strong diffusion bonds by removing oxide from the substrate and increasing interface temperature.

Plasma sprayed tungsten and tungsten-copper coatings are being developed for potential application as plasma facing materials for fusion reactors. Initial spray tests indicated difficulties in tungsten melting and in-flight oxidation. Numerical modeling was performed to help explain these issues. A complex study of the process and its products was performed, including: in-flight diagnostics, characterization of isolated splats, and structure, composition, thermal and mechanical properties of the coatings. Based on these results, the process was optimized, with respect to powder size and various spraying parameters, to improve melting of the particles, reduce oxidation and increase the deposition efficiency.

Yttria stabilized zirconia (YSZ) splats were plasma sprayed on the YSZ substrate preheated to different temperature to examine the influence of the temperature of the underlying surface on which molten droplet impacts on deposition characteristics. The splat morphology and the bonding at the splat-substrate interfaces were examined by SEM. It was found that the crack density decreases rapidly with the increase of the temperature when the splat were formed on an YSZ substrate preheated to above 800°C. The nucleation of YSZ melt on the base of YSZ substrate grains takes place during solidification leading to the formation of the bonding between the splat and substrate when the temperature is increased to over 600°C. The substantial bonding was observed at the interface between YSZ splat and YSZ substrate as the temperature is increased to over 800°C. The results revealed that the temperature of the previous splat on which a molten droplet impacts significantly influence the formation of the interface bonding. In addition, the mechanism and condition for the bonding formation of a splat on a substrate with the identical compositions were discussed.

The paper reports the results of structure examination of intermetallic Fe-Al type coatings obtained by the detonation gun spraying on a C45 plain carbon steel substrate. The structure was analysed with scanning (SEM), transmission (TEM) electron microscopy techniques and electron (SAE) and X-ray diffraction methods as well as quantitative inspection of composition in microareas (EDX). Special attention was paid to the interface between the coating and the substrate analyzing particularly the substructure of the individual grains contained up to 15μm away from the substrate surface layer. The results allowed explaining the formation mechanism of the coating morphology with a contribution of intermetallic phases Fe 3 Al, FeAl, FeAl 2 and Fe 2 Al 5 as well as the ε phase taking into consideration the influence of velocity, temperature and pressure on the powder particles during the D-gun spraying. It was established that the coating produced with the DGS method had sublayer morphology of alternate flattened and partially melted grains with wide range of Al content from 39 up to 63 at.%. Partial melting of the individual powder particles brought about the appearance of the amorphous grains and subsequently columnar crystals of the Fe-Al type phases formed sequentially at the interface area coating and cold substrate surface layer material, which was essential in the mechanism of the Fe- Al coating formation. It was established, that in the area of the polycrystalline dispersive structure formed from the highly plasticized FeAl grains during D-gun spraying, complex oxide films identified as Al 2 O 3 -γ formed, serving as specific composite reinforcement in the intermetallic Fe-Al coating. A mechanism of crystallization of partially melted Fe-Al particle containing nominally 63 at.% Al was carried out in the work in an attempt to explain the formation of different sub-layers within the Fe-Al intermetallic coating at the interface 045 steel surface layer.

Tungsten Carbide (WC) thermal spray coatings have had increased acceptance in commercial aircraft applications driven by the desire to replace chromium electroplate due to environmental and economic considerations [1]. In order to confidently replace chromium electroplate by WC thermal spray coatings, evaluation of wear and fatigue characteristics of the WC thermal spray coatings is necessary. For WC thermal spray coatings to replace chromium electroplate in aircraft applications, the coatings must demonstrate wear and fatigue characteristics as good as or better than those of chrome plating. Previous research in this area has shown that the fatigue life of the WC thermal spray coatings can be improved by inducing compressive stresses in the coating. This paper compares the wear characteristics of several types of WC thermal spray coatings with those of chromium electroplate in sliding wear tests following the "block-on-ring" procedures described in ASTM G77 standard. Wear results are interpreted in terms of coating residual stresses and in terms of X-ray diffraction and Scanning Electron Microscope (SEM) analysis.