Al-Cr-O Protective Coating for Gas Turbine CMAS Resistance
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Solution Overview
Problem
Thermal barrier coatings in gas turbines are prone to degradation due to chemical reactions and penetration by deposits like CMAS, which can lead to coating destruction, and existing methods to prevent this are complex and require multiple process steps.
Innovation Solution
A method using reactive cathodic arc evaporation to apply a homogenous aluminum oxide-based protective coating with controlled oxygen partial pressure and chromium content, forming an Al—Cr—O mixed crystal structure, which can be adjusted for optimal properties and applied in minimal steps, including the option of multiple layers with gradients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional methods are used to prevent CMAS penetration by forming high-melting phases, then protection against CMAS is improved, but the process complexity increases requiring multiple process steps and aftertreatment
Solution Approach 1:
The invention combines multiple protective functions into a single coating layer applied by reactive cathodic arc evaporation. The aluminum oxide-based coating with controlled oxygen partial pressure provides both CMAS resistance and chemical stability in one process step, eliminating the need for separate high-melting phase formation and aftertreatment steps that are required in conventional methods
Solution Approach 2:
The invention changes the process parameters by controlling oxygen partial pressure during cathodic arc evaporation to form a homogenous aluminum oxide-based coating. This parameter control allows the coating to develop desired properties (CMAS resistance, chemical stability) during the deposition process itself, rather than requiring subsequent heat treatment or aftertreatment steps
2Reliability
If multiple process steps and aftertreatment are used to form protective coatings, then coating protection is improved, but the manufacturing time increases
Solution Approach 1:
The invention performs the protective coating formation as a preliminary action during the main manufacturing process. By applying the aluminum oxide-based coating through reactive cathodic arc evaporation before final component assembly or use, the protective function is established in advance, eliminating the need for time-consuming aftertreatment steps that would otherwise be required to achieve adequate protection
Solution Approach 2:
The coating application is merged with the component manufacturing process. The reactive cathodic arc evaporation method allows the protective coating to be deposited as part of the standard surface treatment sequence, combining protection formation with normal manufacturing operations rather than requiring separate, time-intensive post-processing steps
3Manufacturing precision
If a homogenous aluminum oxide-based coating is applied by reactive cathodic arc evaporation, then the coating homogeneity is improved, but the process requires controlled oxygen partial pressure management
Solution Approach 1:
The invention utilizes controlled oxygen partial pressure as a key parameter during reactive cathodic arc evaporation. By precisely controlling the oxygen content in the deposition environment, the process forms a homogenous aluminum oxide-based coating with consistent properties. The parameter control is integrated into the deposition process itself, allowing real-time adjustment to achieve desired coating homogeneity without requiring complex post-deposition processing
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method provides a durable, single-step application of a protective coating that prevents CMAS penetration and chemical reactions, reducing the need for extensive aftertreatment and enhancing the thermal barrier's integrity by forming a corundum structure that adapts to the substrate's properties.
Implementation Method 1
a method for arranging a protective coating, comprising at least one first layer with aluminum oxide content, on a thermally stressed structure by means of cathodic arc evaporation
Implementation Method 2
igniting an arc so that material from the target is evaporated and deposited on the outer side of the thermal barrier coating
Implementation Method 3
providing a controlled oxygen partial pressure in the coating chamber
Implementation Method 4
a protective coating is formed, which protective coating is produced as a result of a diffusion of chromium from a material with high chromium content (protective coating) into a material with low chromium content (thermal barrier coating)
Data Source
AI summary
Provided is a method for arranging a protective coating for a thermally stressed structure, having at least one layer of alpha-aluminium oxide or of element-modified alpha-aluminium oxide, and wherein the protective coating is applied by reactive cathodic arc vaporization. A protective coating produced by the method and a component having a protective coating is also provided.