Preparation of Thermally Spray Coated Specimens

Thermally sprayed coatings (TSC) and thermal barrier coatings (TBC) are widely used on many metal substrates. Invariably, these coatings are not 100 % dense but contain several types of voids, such as porosity and linear detachments. Hot compression mounting is not recommended as the molding pressure can collapse the voids. Use a low-viscosity castable epoxy and use vacuum infiltration to fill the connected voids with epoxy. Fluorescent dyes, may be added to the epoxy. When viewed with fluorescent illumination, the epoxy-filled voids appear bright yellow green. This makes it easy to discriminate between dark holes and dark oxides, as would be seen with bright field illumination. Filling the pores with epoxy also makes it easier to keep the pore walls flat to the edge during preparation. Aside from this mounting requirement, TSC and TBC specimens are prepared using all of the factors needed for good edge retention.

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