This paper evaluates various methods for adjusting the degree of oxidation in arc-sprayed layers. Oxidation control is primarily achieved through the use of a nonoxidizing gas, such as argon or nitrogen, especially in combination with a fine nozzle. In the case of Ni18Cr6Al2Mn deposits, the measured oxide content varied from 0.85 to 3.41 wt% based on the atomizing gas, nozzle, and stand-off distance used. Paper includes a German-language abstract.

HVOF-sprayed alumina appears to be well suited for applications in semiconductor devices. This paper investigates the influence of HVOF spraying parameters on the electrical properties of alumina layers. Diagnostic tests show that small changes in gas ratios and flow rates can significantly alter particle and splat characteristics as well as the dielectric breakdown strength of the coatings. A large number of parameters are changed in order to assess the extent to which electrical properties can be controlled. Paper includes a German-language abstract.

Under load and stress thermal spray coatings have unique behaviour as compared to the bulk materials. The aim of this study was to define the mechanical properties of thermal spray coatings and consider the effect of external stress on coatings under test conditions. Five HVOF or Plasma spray coatings: NiCr, WC-CoCr, Al 2 O 3 -TiO 2 , Al 2 O 3 , and Cr 2 O 3 were studied. Mechanical properties, such as elastic modulus (E), and tensile strength (a) were measured. Behaviour of some coatings in different loading conditions (tension and compressive) was studied.

Three different types of polyethylene powders were flame sprayed onto pre-heated steel substrate previously coated by electrostatic spray system with a thin epoxy primer layer. Properties of the polyethylene (PE) powders, including powder density, particle size and melt flow rate (MFR) were measured in order to study their influence on the mechanical properties of the coating. The spray experiments started with optimization of spraying parameters. The main variables were pre-heating temperature of the substrate, temperature increase during spraying (influenced by the spraying distance), and thickness of the PE coatings. The laboratory tests performed for the coatings were coating characterization by microscopy and mechanical testing. Porosity and thickness of the coatings were determined by optical and stereo microscopy studies from polished cross-sectional samples. Hardness, impact strength, peel strength, and adhesive strength of the coatings were also investigated. Also some hot water sinking and heat cycling tests were performed. As a result from the present studies it can be concluded that powder properties have great influence on the mechanical properties of the final coating.

Partially stabilized zirconia (8Y2O3-ZrO2) coatings were studied as thick thermal barrier coatings (TTBCs) for diesel engine applications. To improve the hot corrosion resistance of TTBCs the 1 mm thick yttria stabilized zirconia coating was densified with aluminum phosphate based sealant. Combined with better hot corrosion resistance other benefits obtained with sealing treatment are improved adhesion as well as increased mechanical properties of the ceramic layer. Three aluminum phosphate based sealants were investigated with varying viscosity level. Different sealant viscosities were used to optimize the level of sealant penetration into the coating. Sealant penetration and the violence of the reaction were determined by XRD, SEM/EDS and optical microscopy. The hardness profile from bond coat to the surface of the top layer was determined. Coating microstructure and phase structure were characterized by optical microscopy and by X-ray diffraction. Microhardness and porosity were determined. Residual stress states were measured by X-ray based stress analyzer. Bond strength of the coatings was determined with tensile test equipment. To simulate the diesel engine combustion conditions, hot corrosion tests were performed for the sealed TTBCs. Hot corrosion resistance of the coating was tested in isothermal exposure of 60Na2SO4 - 40V2O5 melt for 48 hours at 600 °C.