Abstract Fracture mechanical properties of metallic, thermally sprayed layers made of NiCr, NiCrAlY, molybdenum, and NiCrBSi were characterized using an indentation process close to the edge, known as edge chipping. Thermally sprayed layers were assessed according to their relative fracture toughness. The indentation took place in a vacuum chamber of a scanning electron microscope, which enables positioning in the micrometer range and in-situ observation of crack growth. The evaluation of preliminary indentation tests on a choice of thermally sprayed nickel based alloys failed for different indenter geometriy in most cases due to the porosity and the plasticity of the coating material avoiding a defined crack formation and propagation even at very high loads. Scaling down from macroscopic dimension to the micro range is feasible for edge chipping. It can be applied on coatings considering the anisotropic properties parallel and perpendicular to the substrate surface. Paper includes a German-language abstract.

Abstract This paper discusses the relationships between the splat structure and the cohesive and adhesive forces of the layers. The shape and size of splats were examined with a quantitative scanning electron microscope (SEM) examination of the layer surface. Surface morphology was characterized by the distribution of shape and dimension of each splat from the SEM images. The morphologies were quite different among the splats at the center of the spray pattern and those at the peripheral area. The splat morphology at the center of the spray pattern was consisted of the wide spread irregular shaped splats. Cohesive-adhesive strength of coatings sprayed with ordinary process and with the particles passing through the central area of spray pattern were compared. Results obtained show us the splats sprayed with the slit have superior cohesive-adhesive properties compared with those passing through peripheral area of the spray pattern, as expected. Paper includes a German-language abstract.

Abstract This paper investigates the interaction mechanism of ceramic particles and substrate material. Initially, two ceramic powders (pure aluminum oxide and aluminum oxide with 3% by weight of titanium dioxide) are sprayed by detonation spraying and vacuum plasma spraying onto substrates made of stainless steel, on which an electrolytically deposited and subsequently oxidized nickel layer had been applied. The samples are broken after freezing. Then, the interface between layer and substrate as well as the morphologies of the surfaces are examined by means of scanning electron microscopy and X-ray diffractometry. In all samples, regardless of the spraying process, failure is found within the layer and not at the interface, which indicates a high level of adhesion between the ceramic layer and the oxidized nickel substrate. In the case of detonation spraying, the thickness of the layer remaining on the substrate was greater than that of vacuum plasma spraying. Paper includes a German-language abstract.

Abstract By means of homemade ultrasonic arc spraying equipment patented, under the condition of the optimum arc spraying parameters, TiAl alloy coatings were manufactured on the aluminum alloy (LY12) matrix surface. The ultrasonic arc spraying forming process and microstructure of TiAl compounds alloy coatings were investigated by the color metallurgical microscopy, SEM, XRD, EPMA and chemical composition quantitative analysis (ICP). The results showed that TiAl compounds composite coatings can be synthesized by ultrasonic arc spraying system, the coatings possess typical lamella character, consist of TiN (or TiO), TiAl, Ti 0.7.1.1 Al(N,O), Ti 2.4 Al(N,O), Ti 2.4 Al and aluminum alloy solid solution.

Abstract A new method to capture and evaluate the condition of thermal sprayed particles has been developed by using an agar gel target. HVOF sprayed Hastelloy C particles were collected by a gel target placed at the substrate position, i.e., 380mm downstream from the spray nozzle exit. In the surface layer of the target, a large number of fine particles were observed, whereas in the deeper part, globular particles were trapped. The ratio of particles in the surface layer with respect to the deeper part changed by spraying parameters. Furthermore, particles in the target were separated by cutting the gel, collected after resolving the agar, and then observed by SEM. Particles collected from the target's surface layer were fine particles (under 10µm) and fragments of dendritic crystals. These collected from the deeper part were mostly unmelted particles, some of which exposed dendrites. Results obtained by other techniques such as splat observation and in-flight diagnostics are compared with these results. It was concluded that by capturing thermal sprayed particles with a gel target, it is possible to visualize and quantify the melting condition of HVOF sprayed particles.

Abstract New method for characterization of coating microstructures and for evaluation of coating property by means of surface morphology has been proposed. In this paper, the distribution of shape and dimensions of splat was examined using quantitative analysis of scanning electron microscope images from the surface of spray pattern as well as the surface of coating. Results obtained in this study indicate that it is necessary to analyze the spray pattern as well as the surface morphology in order to estimate the coating property by means of the distribution of splat which composes the coating. Moreover, the splats, which are in the interface between the substrate and the coating, should have the same morphology as those of the coating surface. Therefore, the analysis of the surface morphology is important even for the evaluation of coating adhesion behavior.

Abstract Coatings with magnetic properties were produced by vaccum plasma spraying of different Nd-Fe-B powders onto stainless¬steel substrates. Microscopic examination of the coatings in a light microscope revealed a low porosity and a good bonding to the substrate. Scanning electron microscope examinations have shown different phases in these coatings. The magnetic properties of the coatings are also presented. Paper text in German.

Abstract The improvement of the tribologic characteristics of surfaces is an important application of thermal sprayed coatings. Also various ranges of application demand good antiadhesive characteristics. The tribologic and antiadhesive characteristics of fluorine containing polymers are very good. Since furthermore those polymers have the highest thermal resistance of all plastics it has been investigated if those polymers can be integrated in thermal sprayed oxide and carbide coatings. The aim was to improve the tribologic and antiadhesive characteristics. The processes Plasma- and HVOF-spraying have been used to apply the coatings. The polymers in the coatings were detected by examinations with the light-optical and the scanning electron microscope. To heighten the contrast for the light microscopy examinations the metallographic sections of the specimens were physically contrasted. To clearly identify the different phases with the scanning electron microscope EDX-analyses have been carried out. Samples have been tested to investigate the mechanical characteristics of the coatings. Paper text in German.

Abstract This paper aims to characterise and to study several Ni-based alloys bond coatings and to determine the very best spraying conditions to achieve FGMs by means of a single gun with independent powder feed. First, adhesive layers made of NiCr, NiAl, and NiCrAlY were sprayed onto a steel substrate. All samples were tested by isothermal oxidation at 1000 deg C. The oxides formed and the conversions of the original oxides were studied on the samples and characterized using scanning electron microscope and EDS. It is observed that the study of three different bond coating sprayed with the same conditions reveals the best performance for the NiCr coating. Paper includes a German-language abstract.

Abstract The quasi-steady magneto-plasma-dynamic (MPD) arcjet generator is a promising plasma accelerator, which has a coaxial electrode structure similar to those of conventional plasma torches. The MPD arcjet generator utilizes principally electromagnetic acceleration of the interaction between the discharge current of kiloamperes and the azimuthal magnetic field induced by the discharge current, although the working gas is accelerated aerodynamically through a nozzle in a thermal arcjet generator. In this paper, ablation-type MPD arcjet generators are developed for ceramic coatings. Discharge voltages and ablation rates of ceramic materials are examined, and front velocities of ablated atoms of ceramic component are also estimated using a streak camera. The Vickers hardness of coating is measured. Their cross sections are observed with a scanning electron microscope, and their surfaces are analyzed by means of x-ray diffraction and x-ray photoelectron spectroscopy. Paper includes a German-language abstract.

Abstract Laser shock processing (LSP) is a surface treatment similar to shot peening, in which the compressive stresses in the material are created by laser-induced mechanical impacts. The tensions are of sufficient intensity to modify the microstructure and properties. In this paper, the laser pulses are generated with a power density of 5 to 8 GW/centimetres square with a neodymium laser. The glass laser is used to treat Al+SiC composite coatings, which were initially applied using the high-speed oxygen fuel spray technique. The laser-processed samples are prepared metallographically and examined for their microstructure with a scanning electron microscope. The latter is also used to investigate the surface morphology of laser-treated samples. Finally, the microhardness and the vibration wear resistance of the coatings are tested and compared with the data obtained for the samples in the sprayed state. Paper includes a German-language abstract.

Abstract The formation of the microstructure is influenced by a number of parameters. The spray angle is considered to be one of the most important and difficult to control parameters, especially for substrates with complex shapes. In this paper, the influence of the spray angle on the microstructure of gray aluminum oxide and yttrium oxide stabilized (8% by weight) zirconium oxide applications is investigated. Plots are made from each material at four spray angles (90 degree, 70 degree, 55 degree, and 45 degree). Their microstructure is characterized by means of intrusion porosimetry and SEM. The results show clear differences between the two materials. The aluminum oxide microstructure is significantly influenced by the spray angle, while the YSZ microstructure is almost independent of the spray angle. Paper includes a German-language abstract.