The fourth month of Tomáš Tesař at Treibacher Industrie was devoted to spray trials of fine dry powder feedstocks. These powders are candidate materials to fill the gap between the conventional dry coarse powders with the typical particle sizes of tens of micrometers (also sprayed as a reference), and suspension feedstocks with typical particle sizes in the micron or sub-micron range.
Having successfully deposited several coatings with the initial set of parameters, we iterated the process several times in order to bring about microstructural changes, that could be linked to the deposition design in order to understand the peculiarities of the deposition of these largely untested feedstocks.
The knowledge gained within these iterations will be used for the upcoming experiments, in order to:
The illustrative photos show selected coating specimens in as-sprayed state (round white coupons, diameter of 25.4 mm), and embedded in epoxy resin for microstructure observation in SEM (round transparent pucks with specimen cross-sections, diameter of 30 mm). The SEM micrograph shows a cross section of one of the coatings from yttria-stabilized zirconia (YsZ) fine powder feedstock, displaying a dense vertically cracked (DVC) microstructure. Such coatings are used in thermal barrier coating (TBC) systems as the top layers, providing thermal insulation of the structural components from the hot combustion gases in jet engines or gas turbines.
