Ceramic heat barrier coating having low thermal conductivity, and process for the deposition of said coating

a heat barrier coating and ceramic technology, applied in the direction of chemical vapor deposition coating, machine/engine, natural mineral layered products, etc., can solve the problems of differential expansion of metal and ceramic, limited approach, and inability of turbine components such as diffusers to withstand high temperatures, so as to prevent heat conduction through the deposit and reduce the difficulty of application

US20010008708A1Inactive Publication Date: 2001-07-19SN DETUDE & DE CONSTR DE MOTEURS DAVIATION S N E C M A
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Patent Information

Authority / Receiving Office
US · United States
Patent Type
Applications(United States)
Current Assignee / Owner
Publication Date
2001-07-19
Estimated Expiration
Not applicable · inactive patent

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Abstract

A ceramic heat barrier coating is deposited on a substrate so that the coating has a columnar growth pattern which is interrupted and repeated a number of times throughout its thickness by successive regermination of the ceramic deposit. The regermination is obtained by a vapour phase deposition process wherein a polluting gas is introduced intermittently during the deposition of the ceramic. The resulting ceramic coating has a lower thermal conductivity than conventional columnar ceramic coatings.
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Description

[0001] 1. Field of the Invention

[0002] The invention relates to a ceramic heat barrier coating having low thermal conductivity, a process for depositing such a ceramic coating, and to metal articles protected by the coating. The invention is particularly applicable to the protection of hot superalloy components of turbomachines, such as the turbine blades or diffusers.

[0003] 2. Summary of the Prior Art

[0004] The manufacturers of turboengines, whether for use on land or in aeronautics, face constant demands to increase engine efficiency and reduce fuel consumption. One way of addressing these demands is to increase the burnt gas temperature at the turbine inlet. However, this approach is limited by the ability of the turbine components, such as the diffusers and moving blades of the high pressures stages, to withstand high temperatures. Refractory metallic materials known as superalloys have been developed to make such components. These superalloys, which are nickel or cobalt or iron...

Examples

Embodiment Construction

[0031] The invention is based on a finding that a vapour phase deposited ceramic coating has a morphology 1 which changes over its thickness such as shown in FIG. 1. This morphology gradient is marked in particular by a density of mircocolumns 1 which decreases as a function of deposit thickness. The microcolumns are very fine at the interface with the substrate and can be likened to fibres, but tend to flare out in the outer region of the ceramic layer. One of the consequences of the change in the morphology of the ceramic coating with its thickness is that the thermal conductivity of the coating increases with its thickness (see FIG. 2). The outer region of the ceramic coating has a thermal conductivity which is higher than the coating region adjacent the substrate. This effect has been noticed in the case of materials which are very good heat conductors, such as diamond deposited by CVD, and in the case of poorer conductors such as yttriated zirconia. The morphology of a vapour p...