Technological properties of thermally sprayed deposits are to a great extent related to the underlying microstructure. The present project aims to relate macroscopic properties of metallic coatings to their microstructure. For this purpose, thermally sprayed deposits of nickel based alloys (NiCr, NiCrAlY) were manufactured by various spraying techniques - atmospheric and vacuum plasma spraying, flame spraying, high velocity oxygen fuel and water-stabilized plasma spraying. One of the key microstructural features is the void system. This system is usually characterized by the total volume of voids, the so called porosity. An additional characteristic parameter of the void system is the specific surface area. The method of anisotropic Small Angle Neutron Scattering (SANS) in the "Porod Regime" allows the determination of the anisotropic specific surface area of the complex void system that consists of intralamellar cracks and interlamellar pores. In contrast to optical microscopy, the SANS technique is capable of resolving the pore structure down to the nanometer scale, and the measured specific surface area represents a statistically relevant average value for the whole illuminated sample volume which is usually a few mm 3 . Besides the presence of voids and cracks the performance of thermally sprayed coatings is also significantly influenced by residual stresses. In the present work residual strains were determined by the technique of neutron diffraction as well as by bending tests, i.e. laser profilometry of the substrate before and after the spraying process. The specific surface area and the residual stresses are discussed with respect to total porosity, the presence of secondary phases like oxides and wear behavior. Special attention is drawn to the anisotropy of the apparent surface area, which is discussed with respect to the anisotropy of macroscopic properties like electrical resistance.

Improved understanding of microstructure-property relationship can help to shift from experiment-based to science-based development of thermally spray deposits. This should result in shorter and less expensive development as well as in higher functionality and reliability of the deposits. Significant amount of work has been done, however, nearly always studying deposits manufactured by only one of the thermal spray techniques. Results are therefore often spray technique specific. A broad study with samples manufactured by a number of different thermal spray techniques seems to be missing yet. Relationships valid across different techniques should provide better understanding of the generic relationships. This research employs number of different techniques - flame, HVOF, plasma (APS, VPS, WSP), to generate a wide range of microstructures. Various Ni-based alloys are studied starting from a simple chemistry (Ni) and ending with complex NiCrAlY alloys. Presented results were obtained with NiCr (80% Ni, 20% Cr) feedstock. Microstructures are characterized by various techniques-OM, SEM, XRD, small-angle neutron scattering (SANS) and others - to obtain the most comprehensive set of macro to micro structural parameters available today. The wear and corrosion properties of these deposits are measured together with internal coating stresses and the most generic microstructure-property relationships are sought.