The technique was examined to prevent errors during thermal spraying by setting up a spray on-line monitoring system (Spray Watch-2i System) at the starting position in the production line using plasma spraying, and monitoring the characteristics of the particles in the plasma flame between each spraying cycle. The tests were carried out with several spray conditions, changing the gas flow, and the arc current. The state of the plasma flame was measured as the velocity, temperature and flux density of the flying particles. The coating properties were then evaluated by measuring the dielectric breakdown test. It has been found that the evaluation result of the coating correlates very well with the monitoring results of the flame particle characteristics. Therefore there is a possibility that monitoring the state of the particle characteristics within the flame during spraying can control the coating characteristics comparatively easily.

Electrostatic chucks are a potential alternative to vacuum stages used in semiconductor manufacturing. They have no moving parts; just a thin dielectric layer on an aluminum substrate. This paper explains how the dielectric coating for an electrostatic wafer holder was developed, tested, and optimized for commercial use. It describes the materials (Al 2 O 3 -TiO 2 ) and spraying method (VPS) used, the rationale for selecting them, and the metrics on which they are rated. It explains how to verify that the layers have sufficient resistivity, adsorption properties, and thickness to satisfy application requirements. It also discusses the deoxidation of TiO 2 during spraying and its effect on electrical properties. Paper includes a German-language abstract.

The aim of the present work is to study the microstructure of high temperature oxidation and corrosion resistant MCrAlY coatings prepared by high-velocity oxy-fuel (HVOF) spraying and to compare them to vacuum plasma sprayed (VPS) MCrAlY coatings. In this work, CoNiCrAlY, NiCoCrAlYTaReSiHf, and NiCrAlY coatings were prepared on nickel based superalloys by VPS spraying and by two types of HVOF spray process (DJ Hybrid 2600 and JP-5000). The influence of spray parameters, i.e. oxygen flow rate and spray distance, in one of the HVOF processes (DJH 2600) on coating structures and properties were studied also in more detail. The coatings sprayed with different spraying processes were studied in their as-sprayed state and after heat-treatment by optical microscope and scanning electron microscopy (SEM). The results show that selection of appropriate particle size of the spray powder has marked importance in the HVOF process; presence of fine powder particles produce oxides in the coatings and ease clogging of the nozzle in the HVOF gun. The use of appropriate size distribution of the spray powder enables preparation of HVOF MCrAlY coatings with low oxide content and dense structure. The oxide content of HVOF sprayed coatings should be kept as low as possible in order to make the post heat-treatment active in producing a dense microstructure with correct phase structure. The oxide content can be controlled e.g. by flame temperature control by means of oxygen flow rate and by appropriate spray distance selected individually for each powder. Unacceptable high oxide contents in the as-sprayed structures tend to remain unchanged after heat-treatment, whereas well-developed coating microstructure and phase structure are obtained with HVOF sprayed coatings with low oxide content. Microstructures developed in heat-treated VPS and HVOF sprayed coatings are compared.

A hybrid technique that combines plasma spraying and metal diffusion treatment was developed to improve the density, hardness, and adhesion of carbide cermet coatings. In this study, which was conducted to assess the process, Cr3C2-NiCr was deposited on stainless steel substrates by atmospheric plasma spraying. The test specimens were then embedded in a powder mixture of chromium, alumina, and ammonium chloride and diffusion treated. Cross-sectional SEM imaging, X-ray diffraction, and microhardness testing found the resulting surface layer to be extremely dense with outstanding hardness and exceptional bonding strength.