Abstract: A process for removing aluminosilicate-based material (e.g., “CMAS”) from a substrate is described. The material is treated with an aqueous composition containing at least one acid having the formula HXAF6, in which A is Si, Ge, Ti, Zr, Al, and Ga; and x is 1-6. Treatment of the substrate is often carried out by immersion in an aqueous bath. The process is also very effective for removing CMAS-type material from cavities in the substrate, e.g., cooling holes in a gas turbine component. Related compositions are also described.

Abstract: A fuel cell stack includes at least one fuel cell unit and a number of interconnects defining at least two openings and including at least one flow field for flowing a reagent. Each opening defines a respective fuel manifold, including at least one each of intake and exhaust fuel manifolds. The fuel cell unit includes an anode, a cathode, and an electrolyte disposed therebetween. The anode is adjacent to and in both electrical connection and fluid communication with one of the interconnects, which has a flow field that guides a fuel flow between the intake and exhaust fuel manifolds. The cathode is adjacent to and in both electrical connection and fluid communication with another interconnect with a flow field that guides an oxidant flow. The fuel cell stack includes a perimeter isolation seal and at least two interior isolation seals for sealing the electrolyte to the respective interconnects.

Abstract: A thermal barrier coating (TBC 26) and method for forming the TBC (26) on a component (10) characterized by a stabilized microstructure that resists grain growth, sintering and pore coarsening or coalescence during high temperature excursions. The TBC (26) contains elemental carbon and/or a carbon-containing gas that increase the amount of porosity (32) initially within the TBC (26) and form additional fine closed porosity (32) within the TBC (26) during subsequent exposures to high temperatures. A first method involves incorporating elemental carbon precipitates by evaporation into the TBC microstructure. A second method is to directly incorporate an insoluble gas, such as a carbon-containing gas, into an as-deposited TBC (26) and then partially sinter the TBC (26) to entrap the gas and produce fine stable porosity within the TBC (26).

Abstract: An article having a substrate is protected by a thermal barrier coating system. An interfacial layer contacts the upper surface of the substrate. The interfacial layer may comprise a bond coat only, or a bond coat and an overlay coat. The interfacial layer has on its upper surface a preselected, controllable pattern of three-dimensional features, such as grooves in a parallel array or in two angularly offset arrays. The features are formed by an ablation process using an ultraviolet laser such as an excimer laser. A ceramic thermal barrier coating is deposited over the pattern of features on the upper surface of the interfacial layer.

Abstract: A roughened bond coat comprises a screen that includes interwoven wires defining openings and a metallic material disposed on the screen. The screen and metallic material form a roughened bond coat possessing an uneven, undulated, and irregular surface. The metallic material may be one of a slurry and a powder, and applied by coating and spraying, respectively. A thermal barrier coating system, which is formed with and incorporates the roughened bond coat, exhibits greater adhesion of a thermal barrier coating and bond coat due to an increased interfacial surface area provided by the uneven, undulated, and irregular surface.

Abstract: A method of providing a roughened bond coat, for example in a thermal barrier coating system, comprises providing an oxidation-resistant plasma-sprayed layer onto a substrate and disposing a slurry overlayer on the oxidation-resistant plasma-sprayed layer. These steps form a roughened bond coat possessing an uneven, undulated, and irregular surface. A roughened bond coat in a thermal barrier coating system reduces de-bonding of the bond coat and a thermal barrier coating layer, which is desirable to maintain the insulation features of the thermal barrier coating system.

Abstract: A roughened bond coat comprises a screen that includes interwoven wires defining openings and a metallic material disposed on the screen. The screen and metallic material form a roughened bond coat possessing an uneven, undulated, and irregular surface. The metallic material may be one of a slurry and a powder, and applied by coating and spraying, respectively. A thermal barrier coating system, which is formed with and incorporates the roughened bond coat, exhibits greater adhesion of a thermal barrier coating and bond coat due to an increased interfacial surface area provided by the uneven, undulated, and irregular surface.

Abstract: A method of providing a roughened bond coat, for example in a thermal barrier coating system, comprises providing an oxidation-resistant plasma-sprayed layer onto a substrate and disposing a slurry overlayer on the oxidation-resistant plasma-sprayed layer. These steps form a roughened bond coat possessing an uneven, undulated, and irregular surface. A roughened bond coat in a thermal barrier coating system reduces de-bonding of the bond coat and a thermal barrier coating layer, which is desirable to maintain the insulation features of the thermal barrier coating system.

Abstract: An article having a spallation resistant TBC comprises a metal substrate, such as a high temperature superalloy, and a TBC, such as a coating of yttria stabilized zirconia. The TBC comprises a plurality of plasma-sprayed layers. The TBC has a coherent, continuous columnar grain microstructure, wherein at least one layer has a plurality of continuous columnar grains which have been extended by directional solidification into an adjacent layer.

Abstract: A method for smoothing the surface of a ceramic-based protective coating which exhibits roughness is disclosed. The method includes the steps of applying a ceramic-based slurry or gel coating to the protective coating surface; heating the slurry/gel coating to remove volatile material; and then further heating the slurry/gel coating to cure the coating and bond it to the underlying protective coating. The slurry/gel coating is often based on yttria-stabilized zirconia, and precursors of an oxide matrix. Related articles of manufacture are also described.

Abstract: A roughened bond coat comprises a screen that includes interwoven wires defining openings and a metallic material disposed on the screen. The screen and metallic material form a roughened bond coat possessing an uneven, undulated, and irregular surface. The metallic material may be one of a slurry and a powder, and applied by coating and spraying, respectively. A thermal barrier coating system, which is formed with and incorporates the roughened bond coat, exhibits greater adhesion of a thermal barrier coating and bond coat due to an increased interfacial surface area provided by the uneven, undulated, and irregular surface.

Abstract: A composite that protects thermal barrier coatings from the deleterious effects of environmental contaminants at operational temperatures is discovered. The thermal barrier coated parts have least two outer protective coatings that decrease infiltration of molten contaminant eutectic mixtures into openings in the thermal barrier coating.

Abstract: A method of providing a roughened bond coat, for example in a thermal barrier coating system, comprises providing an oxidation-resistant plasma-sprayed layer onto a substrate and disposing a slurry overlayer on the oxidation-resistant plasma-sprayed layer. These steps form a roughened bond coat possessing an uneven, undulated, and irregular surface. A roughened bond coat in a thermal barrier coating system reduces de-bonding of the bond coat and a thermal barrier coating layer, which is desirable to maintain the insulation features of the thermal barrier coating system.

Abstract: An article having a spallation resistant TBC comprises a metal substrate, such as a high temperature superalloy, and a TBC, such as a coating of yttria stabilized zirconia. The TBC comprises a plurality of plasma-sprayed layers. The TBC has a coherent, continuous columnar grain microstructure, wherein at least one layer has a plurality of continuous columnar grains which have been extended by directional solidification into an adjacent layer. In a preferred embodiment, the coherent, continuous columnar microstructure comprises substantially all of the volume of TBC. A coherent, continuous columnar grain microstructure is also taught wherein at least some of the plurality of coherent, continuous columnar grains which comprise a TBC extend through essentially the entire thickness of the coating.

Abstract: A method for providing a substantially-smooth protective coating on a metal-based substrate is disclosed. It comprises the steps of: (a) applying a thermal barrier coating over the substrate by plasma-spraying; (b) plasma-heating the applied coating according to a time- and temperature schedule sufficient to re-melt the surface region of the coating, allowing it to flow and smoothen; and then (c) cooling the surface region to a temperature below its melting point. The thermal barrier coating is often zirconia-based, e.g., yttria-stabilized zirconia. After being cooled, the surface is much smoother than when originally applied, thereby allowing the coating to be used in a higher-temperature environment.

Abstract: A method for providing a substantially-smooth protective coating on a metal-based substrate is disclosed. A thermal barrier coating is first applied over the substrate by plasma-spraying. The coating is then plasma-heated according to a time- and temperature schedule sufficient to re-melt its surface region, allowing the coating material to flow and smoothen. The surface region is then allowed to cool to a temperature below its melting point. After being cooled, the surface is much smoother than when originally applied, which allows the coating to be used in a higher-temperature environment. The coating is often zirconia-based, e.g., yttria-stabilized zirconia.

Abstract: A method for improving the quality of a zirconia-based coating deposited on a metal-based substrate is disclosed. The method comprises the step of plasma-spraying zirconia powder of substantially uniform particle size onto the substrate. The disclosure further relates to an improved powder source material for use in a plasma. The source material is zirconia powder having a uniform particle size, and optionally, a uniform particle density. The use of such a material results in improved thermal barrier coatings for various substrates, such as those found in a turbine engine.

Abstract: A method and apparatus form a thermal barrier coating on a metal component. A molten thermal barrier coating powder is sprayed on the component in sweeping strokes. A plurality of overlapping solidified coating ribbons are deposited on the component and include a sequentially deposited surface ribbon forming sublayer ribbons therebelow. The surface ribbon is preheated at a spray site so that the sprayed molten powder remelts the surface ribbon at the spray site for sequentially welding the sequentially deposited surface ribbons to the sublayer ribbons.

Abstract: A composite that protects thermal barrier coatings from the deleterious effects of environmental contaminants at operational temperatures is discovered. The thermal barrier coated parts have least two outer protective coatings that decrease infiltration of molten contaminant eutectic mixtures into openings in the thermal barrier coating.

Abstract: A method and apparatus form a thermal barrier coating on a metal component. A molten thermal barrier coating powder is sprayed on the component in sweeping strokes. A plurality of overlapping solidified coating ribbons are deposited on the component and include a sequentially deposited surface ribbon forming sublayer ribbons therebelow. The surface ribbon is preheated at a spray site so that the sprayed molten powder remelts the surface ribbon at the spray site for sequentially welding the sequentially deposited surface ribbons to the sublayer ribbons.