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METHOD FOR SELECIVELY TAPERING EBCs

IP.com Disclosure Number: IPCOM000246510D
Publication Date: 2016-Jun-14
Document File: 8 page(s) / 49K

Publishing Venue

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Abstract

The invention relates to environmental barrier coatings (EBCs) used on ceramic gas turbine engine parts. Specifically, a method for selectively removing slurry in order to taper the EBC thickness is disclosed.

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METHOD FOR SELECIVELY TAPERING EBCs

TECHNICAL FIELD

    The invention relates to environmental barrier coatings (EBCs) used on ceramic gas turbine engine parts. Specifically, a method for selectively removing slurry in order to taper the EBC thickness is disclosed.

BACKGROUND

    Higher operating temperatures for gas turbine engines are continuously sought in order to increase their efficiency. However, as operating temperatures increase, the high temperature durability of the components of the engine must correspondingly increase. Significant advances in high temperature capabilities have been achieved through formulation of iron, nickel and cobalt-base superalloys. While superalloys have found wide use for gas turbine components used throughout gas turbine engines, and especially the higher temperature sections, alternative lighter weight substrate materials have been proposed and sought.

    Ceramic materials containing silicon, such as those comprising silicon carbide (SiC) as a matrix material and/or as a reinforcing material (e.g., as fibers) are currently being used as substrate materials for higher temperature applications, such as gas turbine engines, heat exchangers, internal combustion engines, etc. These silicon-containing matrix/reinforcing materials are commonly referred to as ceramic matrix composites (CMCs). These silicon- containing materials used as matrix materials and/or as reinforcing materials can decrease the weight yet maintain the strength and durability of turbine components comprising such substrates, and are currently being considered for many gas turbine components used in higher


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temperature sections of gas turbine engines, such as turbine components comprising airfoils (e.g., compressors, turbines, vanes, etc.), combustors, and other turbine components for which reduced weight is desirable.

    As operating temperatures increase, the high temperature durability of such CMC materials must also correspondingly increase. In many applications, a protective coating is beneficial or required for such silicon-containing substrates. Such coatings should provide environmental protection by inhibiting the major mechanism for degradation of silicon- containing materials in a corrosive water-containing environment, namely, the formation of volatile silicon monoxide (SiO) and silicon hydroxide (Si(OH)4) products. Consequently, a necessary requirement of an environmental barrier coating (EBC) system for a silicon-containing substrate is stability in high temperature environments containing water vapors. Other important properties for these coating systems can include a coefficient of thermal expansion (CTE) compatible with the silicon-containing substrate, low permeability for oxidants, low thermal conductivity, and chemical compatibility with the silicon-containing substrate and overlaying silica scale formed typically by oxidation.

    Examples of EBCs are described in U.S. Patent No. 8,673,400 to Kirby at al. The EBCs...