Water based environmental barrier coatings for high temperature ceramic components

Abstract

Environmental barrier coatings for high temperature ceramic components including: a bond coat layer; an optional silica layer; and at least one transition layer including: from about 85% to about 100% by volume of the transition layer of a primary transition material selected from a rare earth disilicate, or a doped rare earth disilicate; and from 0% to about 15% by volume of the transition layer of a secondary material selected from Fe₂O₃, iron silicates, rare earth iron oxides, Al₂O₃, mullite, rare earth aluminates, rare earth aluminosilicates, TiO₂, rare earth titanates, Ga₂O₃, rare earth gallates, NiO, nickel silicates, rare earth nickel oxides, Lnb metals, Lnb₂O₃, Lnb₂Si₂O₇, Lnb₂SiO₅, borosilicate glass, alkaline earth silicates, alkaline earth rare earth oxides, alkaline earth rare earth silicates, and mixtures thereof; where the transition layer is applied to the component as a slurry including at least water, the primary transition material and at least one slurry sintering aid, and where a reaction between the slurry sintering aid and the primary transition material results in the transition layer having a porosity of from 0% to about 15% by volume of the transition layer.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This Application claims priority to U.S. Provisional Application Ser. No. 61 / 230,262, filed Jul. 31, 2009, which is herein incorporated by reference in its entirety.TECHNICAL FIELD[0002]Embodiments described herein generally relate to water based environmental barrier coatings for high temperature ceramic components. More particularly, embodiments herein generally describe water based environmental barrier coatings comprising sintering aids for use on high temperature ceramic components.BACKGROUND OF THE INVENTION[0003]Higher operating temperatures for gas turbine engines are continuously being sought in order to improve 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 the formulation of iron, nickel, and cobalt-based superalloys. While superalloys hav...

AI Technical Summary

Benefits of technology

[0006]Accordingly, there remains a need for environmental barrier coatings to protect CMCs from the high temperature steam environments present in gas turbine engines.

Problems solved by technology

However, as operating temperatures increase, the high temperature durability of the components of the engine must correspondingly increase.

Additionally, silicon oxide is not stable in high temperature steam, but rather, can be converted to volatile (gaseous) silicon hydroxide species.

Unfortunately, there can be some undesirable issues associated with standard, industrial coating processes such as plasma spray and vapor deposition (i.e. chemical vapor deposition, CVD, and electron beam physical vapor deposition, EBPVD) currently used to apply EBCs.

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