Abstract This paper aims to evaluate various measurement methods that characterize the elastic layer behavior. The use of thermally sprayed multilayer composite materials for mechanically and/or thermally highly stressed components has proven itself in a wide variety of areas of modern mechanical and plant engineering. The mechanical operating behavior of layered composite materials is determined by the interplay of residual stresses and load stresses as well as the existing bond strength. The determination of the Young's modulus in thermally sprayed coatings is, however, a difficult task because of the limited coating thickness, their brittleness and the very inhomogeneous microstructure consisting of nonequilibrium phases, oxidation products, cracks, and pores. Two different investigations routines were performed, first the investigation of the influence of the indentation load on the determined Young's modulus and second the influence of the analysis program. Paper includes a German-language abstract.

Abstract Among candidate materials for plasma spraying titanates ATiO3, where A is an element from the alkaline earth group (11), were not systematically tested until today. This paper reports on plasma spraying of synthetic perovskite CaTiO3 and geikielite-perovskite system MgTiO3-CaTiO3. Perovskite CaTiO3 is well known as dielectric material and a basic component of complex dielectric ceramics. Since it is relatively chemically simple and inexpensive material it has been selected for the basic preliminary studies. Mixture of geikielite-perovskite MgTiO3-CaTiO3, with Mg:Ca ratio equal to 94:6, was chosen because its permittivity is independent of temperature. Plasma spraying was done with the water stabilized plasma gun WSP. Plasma spraying conditions were optimized using single splat observation for various substrates and varying substrate temperature. Standard experimental techniques were used for studying of microstructures, chemical and phase compositions and porosity of as-sprayed and annealed deposits. Mechanical properties such as Young’s modulus and microhardness were measured.

Abstract Yttria stabilized zirconia particles are plasma sprayed on polished stainless steel substrate. Starting powders are fused and crushed powder, and hollow spherical powder. Four types of the splat morphology, which are splash, rugged, gravel mounted, and disk splats, are observed. Splash and disk splats are fully melted particles, but rugged and gravel mounted like splats are partially melted particles Gravel mounted like splat is observed from only hollow spherical powder, and disk splat is observed in the case of high substrate temperature. It is found that the ratio of splat morphology changes with spraying parameters. Porosity of the coating from fused and crushed powder is higher and Young's modulus of that is lower than that from hollow spherical powder. The ratio of rugged and gravel mounted splats affect porosity and Young's modulus. Adhesive strength increases with the increase in the ratio of disk splat. So, the coating properties are improved by controlling splat morphology. KEYWORDS: Splat Morphology, Partially Melted Particle, Disk Splat, Porosity, Young's Modulus, Adhesive Strength

Abstract Spinel powders of different compositions were fabricated for their good properties of chemical resistance. These powders were plasma sprayed on steels and their microstructure was investigated by scanning electron microscopy (SEM), microanalysis, X-ray diffraction and transmission electron microscopy (TEM). Due to the powder fabrication process, coatings were very heterogeneous in composition, but had the spinel structure. TEM observations pointed out that splat solidification occurred with a cooling rate gradient leading to different crystallization inside a lamella. Young's moduli by the coatings were measured by the resonant frequency method and the correlation with coating microstructure was discussed.

Abstract The Young's modulus of the ceramic top coat of a plasma sprayed thermal barrier coating (TBC) has been reported to vary by as much as a factor of three with changes in processing parameters and by as much as a factor of four due to prolonged thermal exposure. Since the residual stress is expected to vary directly with the modulus of the ceramic layer, it follows that a change in modulus will change the residual stresses in the ceramic layer. The objective of this study was to evaluate the modulus of plasma sprayed coatings as a function of thermal cycle exposure and silica content of the ceramic. The study employed the Cantilever Beam Bending Method to examine Young's modulus for an yttria stabilized zirconia TBC applied by plasma spraying, for zero and ten thermal cycles and for silica contents of 0.1% and 1.0%. Results are discussed in terms of mechanisms that may affect modulus and the effect of modulus variations on residual stresses.

Abstract Mechanical properties of water stabilized plasma spray-formed Al 2 O 3 -13wt%TiO 2 have been investigated by using indentation techniques and a four-point bend test. Young's modulus was determined by four point bend, nano- and Knoop indentation tests. Modulus of rupture was measured by the four-point bend test. The anisotropic behavior as well as the reduced Young's modulus and strength of thermal spray deposits are extensively investigated and can be related to the unique microstructure; i.e., the spheroidal shape of pores, cracks and splats as well as inter-lamellar boundaries. The heat treatment substantially enhanced the mechanical properties and the microstructure becomes more homogeneous and isotropic; that is, the deposits lose their unique nature and become more similar to bulk materials.