Cold atmospheric plasma spraying is used to produce thin coatings of copper and tin between 20-80 μm thickness for use in diffusion soldering. This study presents an alternative process to apply composite solders directly onto power electronic bare dies. The formation of intermetallic phases may be promoted by the homogeneous distribution of the Cu and Sn particles as they are presented not in a layered structure but as a pseudo alloy within the coating. The Cu and Sn powder is mixed in situ using two powder conveyors, enabling adjustable mix ratios. The presented approach has been shown to produce a homogeneous particle distribution within the coating. Furthermore, preliminary experiments indicate the feasibility of the technology for applications in diffusion soldering.

In this study, cold sprayed Cu approximately 40 to 60 μm in thickness is deposited on 6063 and LD10 aluminum plate to improve wettability for low temperature soldering and to serve as a barrier layer to protect the substrate from gallium diffusion originating in the solder paste. The effect of the coating on wettability, diffusion, solder joint interface microstructure, and shear strength is investigated in detail.

In principle, coatings made by brazing is a process variant of brazing which can be classified as high-temperature brazing. It is a thermal process which is carried out either without flux in a vacuum or under inert gas with tapes/slurries/pastes/powders with a liquidus temperature generally above 900 °C. In this process, no components are firmly connected to each other but brazeable materials are applied which, after the heat treatment process, produce a metallic, material-tight coating. The most commonly used filler matrix materials are nickel-based ones, cobalt, iron, copper-based ones or corresponding alloys. Hard materials are mixed in depending on the coating function. Carbides, silicides, borides, oxides, diamonds, CBn or hard material mixtures can be used as hard materials. Common industrial used hard materials are WC, CrC or NbC. Hard material proportions in the coating can be up to 80 Vol.%. Actual developments show contents up to 90 Vol.% and more. Depending on the application, layer matrix hardnesses are flexibly adjustable from 20-30 HRC to 62-65 HRC. The coating produced can therefore perform various functions. For this reason, they are also called functional coatings. For example, hard material particles introduced into the matrix can be firmly brazed onto the surface of the component and thus take on a wear protection or gripping function. Alternatively, worn components such as moulds or turbine blades can be recontoured by brazing suitable materials as tapes or slurries into the wear areas and then reworking them. The coatings are very dense and crack-free and are therefore also very suitable for corrosion protection, even at high temperatures. In contrast to deposit welding, the deposit-brazed coatings are relatively smooth and often do not need to be reworked or ground. The strength of high-temperature brazed hard material coatings can reach the strength of the base materials. This results in a highly stressable layered composite. 2D and 3D geometries can be coated both internally and externally. Coating thicknesses are usually ranging from 1.0 up to 4.0 mm. Minimum layer thicknesses of 0.05-0.1 mm up to 10 mm and more can be achieved. Recent developments also show the possibility of locally brazing on applied tapes or suspensions using laser energy without having to heat the entire component. By selecting appropriate morphologies of the starting powders for braze matrix materials and hard materials, the coating system can be specifically optimised and adapted for the respective application. In addition, work is being carried out on systems in which "signaling elements" are incorporated into the coating in order to record the condition of a surface during operation. For example, forces, wear or temperature. The lecture gives an overview of selected processes, materials and applications and an outlook on new developments.

High-pressure die casting (HPDC) is a well-established manufacturing process used in the automotive sector to make high-precision components. The necessity to reduce fuel consumption increases the use of low-density components in the automotive industry. Corrosion induced by molten metal is one of many failure modes for dies, changing the die's geometry and surface roughness. All combined wear changes the dimensional precision of the manufactured parts but also the surface quality of the components. Many additive deposition methods are applied to decrease wear and recover the surface. Thermally sprayed coatings can improve the surface properties and recover the geometry of the die caused by the aluminum attack. The main objective of this work is to observe the behavior of the H13, Cr3C2-25NiCr, and WC10Co4Cr coatings deposited by HVOF and HVAF, tested against Aluminum corrosion and Die-soldering tests. After dissolution, the chromium carbide reacts with the aluminum, creating a tough intermetallic interface, and raising the extraction tensile stress. After Aluminum corrosion tests, it was observed that the WC 10Co 4Cr HVAF coating presented low adhesion to the aluminum with no observed coating failure due to the formation of intermetallic. Die soldering tests indicated that the WC 10Co 4Cr protects the substrate, resulting in lower extraction tensile stress than H13 base material and other HVOF coatings. It was possible to observe that WC 10Co 4Cr HVAF coating showed results comparable to AlCrN PVD coating.

Application of cold gas spraying for deposition of braze filler coatings is investigated. Different light weight alloy substrates, i.e. aluminum AA1050, AA3005, AA5754 and AA7022, magnesium AZ91 and titanium TiAl6V4, are used. Filler coating materials depend on the substrate melting temperature. So for aluminum alloys Al12Si and zinc based fillers, for AZ91 pure zinc and for Ti6Al4V different Cu-Ni blends are applied. CGS process parameters are varied with regard to process gas (nitrogen) temperature and pressure, powder feed rate and spray distance. Correlation to process characteristics and economical aspects are given. The usability of the produced filler coatings is shown by different optimized brazing/soldering processes. In case of aluminum braze joints a full metallographical investigation is carried out by optical and scanning electron microscopy as well as EDXS analyses. The gathered results are compared with those of conventional filler material addition, i.e. wire, roll plating and foil.

In this work, steel columns are metallurgical bonded to tempered glass with the aid of atmospheric plasma spraying and low-temperature soldering. Glass surfaces were sandblasted using different grain sizes, then multilayer (Al 2 O 3 -Cu) coatings were applied at various power levels and spraying distances. Sn-Ag-Cu solder paste was then painted on the metallized glass and steel structures were set in place and soldered in a reflow oven. The interfacial bond strength of the alumina layer was measured along with the strength of the solder joint. The results are presented and correlated with sandblasting grain size and spraying heat input.

Assemblies containing fiber-reinforced plastic (FRP) and metal parts are typically fastened together via mechanical joining or adhesive bonding. Mechanical joining processes tend to weaken FRP parts by cutting fibers, while adhesives require long cures and often lead to inseparable material compounds. This paper evaluates a new joining method in which plastic parts are laser treated, then metallized via wire-arc spraying, and finally soldered to mating metal parts using a low-temperature process. Due to the effective increase in interface area resulting from laser structuring, bond strengths of up to 15.5 MPa can be achieved.

Thermal spraying for joining and filling of aluminum substrates under atmospheric conditions represents an enrichment in soldering technology. In a respective process, rod-, wire- or cored wire type, zinc-aluminum-based spray materials are applied for joining components or area filling of substrate and fused simultaneously. The advantages, in contrast to soldering, result from the direct application of the spray material, in particular also in constraint positions, and an uncomplex processing, which enables a conditioned inline capability and the use as a comparatively simple procedure for construction-site services or repairs. The aluminum substrate surface and spray material passivation, which would prevent a successful fusing, can be effectively suppressed by the use of a flux in the cored wires as well as straight on the substrates or a brushing activation.

This study assesses the potential of kinetic-spray coatings for dealing with the effects of soldering and erosion on aluminum casting dies. In the experiments, molybdenum-boride cermet and cobalt-based alloy powders are cold sprayed onto SKD61 substrates. Coating microstructure is assessed via SEM and XRD analysis and several mechanical properties are measured. In order to evaluate soldering resistance, the coatings are immersed in a molten aluminum bath. Although cold-sprayed CoCrNiWC exhibited high coating density and low porosity, its soldering resistance was significantly lower than that of MoB-NiCr. The boride cermet coating not only exhibited superior soldering resistance, but also higher hardness, bond strength, and wear resistance. However, its deposition efficiency needs further improvement.

The main advantage of the cold spray process is minimal influence on the substrate properties with sufficiently high bond strength. This advantage allows metal coating to be applied to the specific objects which were never subjected to the thermal spray process. The examples of the low pressure cold spray application to the glass objects, magnet sensors and electronic elements are presented and discussed.

Very low pressure plasma spraying (VLPPS) processes operate at a pressure of approximately 100 Pa, where the interaction of the plasma jet with the surrounding atmosphere is very weak and, as a result, plasma velocity is almost constant over a long distance from the nozzle exit. At these low pressures, the collision frequency is distinctly reduced and the mean free path is strongly increased. As a consequence, the specific enthalpy of the plasma is substantially higher, but at lower density. These particular plasma characteristics offer enhanced possibilities to spray thin and dense ceramics compared to conventional processes which operate in the pressure range between 5 and 20 kPa. This paper presents examples of gas-tight and electrically insulating layers with thicknesses less than 50 μm for solid oxide fuel cell applications. Plasma spraying of oxygen conducting membrane materials like perovskite is also discussed.

Flame sprayed Al-12Si coatings were produced onto the surface of composite castings parts in order to enhance the adhesion of such castings. Due to the high surface roughness and the presence of pores in the coatings combined with the formation of an intermetallic phase at the interface, the adhesion of flame sprayed composite castings could be enhanced by a factor of 2 in comparison to blank castings and by a factor of 1.3 when compared to sand-blasted castings. However, results also show that gaps are mostly present at the interface between the Al profiles and the flame sprayed coatings and these gaps have a negative effect on the adhesion values of the composite casting parts. Therefore, an optimization of the adhesion of the coating on the Al profiles through an optimization of both the sand-blasting and the flame spraying parameters would be beneficial for further enhancement of the adhesion of composite casting parts.

Due to its low weight and excellent dimensional stability, carbon fibre-reinforced carbon (C/C) gains more and more importance as construction material for light-weight charging racks in industrial furnaces. However, for high-temperature applications above 1,000 °C, C/C has to be protected with a diffusion-inhibiting coating in order to avoid an undesired carburization of components which are in contact with the charging rack. In the present work, coatings were produced by means of atmospheric plasma spraying (APS) and powder flame spraying (PFS). The ceramic powders Al 2 O 3 , Al 2 O 3 /Cr 2 O 3 , Al 2 O 3 /TiO 2 and yttria stabilized zirconia (YSZ) were used as coating materials, while molybdenum and silicon carbide served as adhesion-promoting intermediate layers. In order to reduce the residual stresses in the ceramic coatings, specimens with a defined segmented surface structure were compared with conventional closed coatings. Long-term high-temperature tests in several atmospheres were conducted on laboratory scale as well as in industrial practice.

Die-casting moulds are subjected to severe conditions of cyclical thermal and mechanical loads, as well as chemical and mechanical wear. Dies mostly fail due to a combination of wear mechanisms. Heat checking, erosion, melt corrosion and soldering often lead to complete die failure. Ceramic plasma-sprayed coatings have a great potential for die protection, since they are chemically inert, and show high form stability at elevated temperatures. Furthermore, they show good resistance against thermal shock due to the porous state of the coated layer and low Young’s modulus. In the present study, the influence of hot isostatic pressing on thermal fatigue resistance of plasma spraying coatings is investigated. Thermal and thermomechanical tests were applied to characterise their ability to protect dies. The coatings were evaluated by residual stress measurements, metallography, hardness test and X-ray diffraction.

This paper investigates the influence of plasma spraying parameters on the gas tightness and ionic conductivity of YSZ electrolyte layers in thin-film solid oxide fuel cells. Measurement data obtained from the layers are correlated with electrochemical test results, providing helpful information on how the performance of SOFC stacks can be improved. Paper includes a German-language abstract.

In this study, plain carbon steel wire and pure iron powder are deposited on grit-blasted Fe-Si alloy substrates using thermal (electric arc, plasma, and HVOF) and kinetic spraying techniques. The coatings obtained were then heat treated. Coating microstructures and mechanical properties were investigated and compared focusing on oxidation, delamination, and Si dilution from the substrate to the coating.

Sufficient electrical insulation must be ensured between the individual connection plates made of the ODS alloy in planar high-temperature fuel cells. In this paper, APS coatings and coating systems consisting of zirconium dioxide or zirconium dioxide/aluminum oxide are sprayed onto structured plates made of ODS-chromium alloy, qualified and implemented. The electrical insulation of both the coatings and the sealing glass composites is determined at 850 deg C and 950 deg C. The gas resistance of the coated sealing glass composite samples to air, hydrogen and hydrogen/water is determined experimentally. The coating technology is developed for small series production and successfully implemented on a large joined multi-cell unit with basic dimensions of 260 x 260 millimeter square. The paper demonstrates that this coating technology is sufficiently developed for industrial applications. Paper includes a German-language abstract.

Pulsed plasma transferred arc surfacing is presently used in many industrial applications to make protective layers against corrosion, temperature exposition, and excessive wear. Increasing wear resistance is especially important in areas of industry where titanium alloys are used, such as aviation and cosmonautics, because the wear resistance of titanium alloys is often weak. One way to increase the wear resistance is to deposit or form a cermet with a titanium matrix (TMC) on the surface of the part. The present study deals with the fabrication and characterization of TMC based on B4C. TMC with B4C was formed by cofeeding Ti6Al4V and B4C powder into a melting pool. It has been found that the deposited, relatively thick layers have homogeneously dispersed B4C grains in the matrix. The deposits are metallurgically connected to the substrate - Ti6Al4V. The TMCs were investigated in terms of microstructure and chemical composition. Wear resistance was determined using the linear pin test.

There are several challenges when designing components exposed to harsh environments. Cases such as hydraulic turbines and marine propellers are classic examples of demands for materials capable of withstanding erosion and corrosion wear. To enhance and recover worn surfaces, it is usual the use of coatings. This study proposes a new series of coatings based on diffusional effects observed for thermally sprayed chromium carbide coating. A columnar morphology was observed, due to the diffusional gradient perpendicular to the surface. The coating has also shown an absence of porosity and peculiar properties.

In Laser Cladding, a differentiation must be made between cladding by brazing and cladding by welding regarding process parameters and the resulting material properties. Results of investigations of bronze cladding on steel parts produced by Laser Deposition Brazing will be presented. This means that a strong metallurgical bond is realized by diffusion processes by Laser Deposition Brazing, but the steel base material is not molten. The coatings were characterized by hardness distribution measurements from the bronze cladding to the steel substrate, by measuring the size of the heat-affected zone and by porosity measurements. This combination of a steel substrate and a local bronze coating is used industrially in many tribological applications, such as plain bearings or hydraulic pumps etc. The bronze offers excellent tribological properties. In some cases, the bronze is used as a complete solid part. However, applying the bronze locally to a steel base body instead of using a complete solid bronze component, offers the advantage of the higher modulus of elasticity of the steel, which provides greater stability of shape with regard to possible elastic deformations as these coated parts are exposed to high mechanical loads, it is essential that a high coating quality is achieved by laser cladding and that the properties are extensively and purposefully characterized. The production technology, the characterization and the industrial applications of such bronze coated steel parts are presented and explained in this contribution.