Optimized high purity coating for high temperature thermal cycling applications

Abstract

The invention is directed to a blended material and method for obtaining thermal barriers for high temperature cycling applications that have both high sintering resistance to achieve a high service lifetime and low thermal conductivity to achieve high operating temperatures. These materials are additionally suited for use in high temperature abradable (rub seal) coatings. The invention provides desired coating structures so that the changes in the coating microstructure over the in-service lifetime are either limited or beneficial.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority under 35 U.S.C. § 119(e) from U.S. Provisional Patent Application No. 60 / 724,286, filed on Oct. 7, 2005, which is incorporated herein by reference.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT [0002] Not Applicable REFERENCE TO A “MICROFICHE APPENDIX”[0003] Not Applicable BACKGROUND OF THE INVENTION [0004] 1. Field of the Invention [0005] The invention relates to ceramic materials for thermal barriers and abradable coating systems in high temperature and high temperature cycling applications, and more particularly to ultra-pure zirconia and / or hafnia materials for use in thermal barrier and abradable coating applications. [0006] 2. Description of the Related Art [0007] Superior high-temperature properties are required to improve the performance of heat resistant and corrosion resistant members. These members include, for example gas turbine blades, combustor cans, ducting and nozzle gui...

AI Technical Summary

Benefits of technology

[0014] One aspect of the invention is to provide a blend of ceramic materials for use in high-temperature thermal barriers or abradable seal coatings that have reduced sintering rates in addition to photon blocking or scattering characteristics. One material comprises of zirconia and/or hafnia and ytterbia (Yb2O5) and/or yttria (Y2O3), having a total amount of impurities of less than or equal to 0.15 weight percent, and preferably less than or equal to 0.10 percent. The zirconia and/or hafnia is partially stabilized by the ytterbia and/or yttria, and the specific oxide impurity concentrations of the material do not exceed 0.1 weight percent soda, 0.05 weight percent silica, and 0.01 weight percent alumina and 0.05 weight percent titania and preferably 0.01 weight percent soda, 0.01 weight percent silica, and 0.01 weight percent alumina and 0.01 weight percent titania. Another material comprises of zirconia and/or hafnia and neodymia (Nd2O3) and/or europia (Eu2O3), having a total amount of impurities of less than or equal to 0.15 weight percent, and preferably less than or equal to 0.10 percent. The zirconia and/or hafnia is partially stabilized by the neodymia and/or europia, and the specific oxide impurity concentrations of the material do not exceed 0.1 weight percent soda, 0.05 weight percent silica, and 0.01 weight percent alumina and 0.05 weight percent titania and preferably 0.01 weight percent soda, 0.01 weight percent silica, and 0.01 weight percent alumina and 0.01 weight percent titania.

[0015] In one aspect of the invention, a blended high-purity coating that is suitable for high temperature cycling applications is provided. The coating includes a first material and at least a second material. The first material is essentially about 4 to 20 weight percent of a stabilizer of one or more rare earth oxides, and a balance of at least one of zirconia (ZrO2), hafnia (HfO2) and combinations thereof, wherein the zirconia (ZrO2) and/or hafnia (HfO2) is partially stabilized by the stabilizer. The second material is of a different composition than the first material, and is also about 4 to 20 weight percent of a stabilizer of one or more rare earth oxides, and a balance of at least one of zirconia (ZrO2), hafnia (HfO2) and combinations thereof, wherein the zirconia (ZrO2) and/or hafnia (HfO2) is partially stabilized by the stabilizer. The first and second materials are blended together in the coating, and the total amount of impurities in the coating is less than or equal to 0.15 weight percent.

[0016] In another aspect of the invention, a high-purity coating structure that is suitable for high temperature cycling applications is formed by a process of the following steps: providing a first material in a form suitable for use in thermal spraying applications, wherein said first material is about 4 to 20 weight percent of a stabilizer of one or more rare earth oxide

Problems solved by technology

An additional design criteria for gas turbines is increased operating time between maintenance and repairs, meaning longer lifetime of the materials used in these applications.

If there were no cracks in the coating, the thermal barrier would not function, because the differences in thermal expansion between the metal substrate system and the coating will cause interfacial stresses upon thermal cycling that are greater than the bond strength between them.

In addition to this, cracks are also formed during service, so the structure

Images