PEO Coating for Gas Turbine Stator Vanes
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Solution Overview
Problem
Conventional anodized aluminum coatings on stator vanes deteriorate in acidic or alkaline environments, leading to corrosion and poor erosion resistance, exposing metallic parts to further damage.
Innovation Solution
A plasma electrolytic oxidation (PEO) process is used to form a thick, crystalline aluminum oxide layer on aluminum components, which is then sealed with a crosslinked polymer or chromate coating, enhancing corrosion and wear resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional anodized aluminum coating is used on stator vanes, then the coating can be rapidly applied and provides corrosion resistance under normal conditions, but the coating deteriorates in acidic or alkaline environments leading to intergranular attacks and poor erosion resistance
Solution Approach 1:
The patent changes the fundamental parameters of the aluminum oxide coating by controlling the anodization process to produce a specific pore structure and oxide layer composition. This includes adjusting voltage, current density, temperature, and electrolyte composition to create an oxide layer with enhanced chemical stability and reduced reactivity toward acidic and alkaline environments
Solution Approach 2:
The patent creates a composite protective system consisting of the aluminum oxide anodized layer combined with a sealant coating. The sealant penetrates the porous structure of the anodized layer and forms a composite barrier that provides both corrosion resistance and erosion resistance, while the underlying anodized layer provides structural integrity and additional corrosion protection
2Ease of manufacture
If conventional anodized aluminum coating is used, then the coating process is simple and inexpensive, but the coating is worn off easily in erosive environments exposing metallic parts to corrosion
Solution Approach 1:
The patent applies preliminary protective measures by first creating the anodized aluminum oxide layer which serves as a stable, adherent base coating. This preliminary layer is then sealed with a protective sealant coating before the component is put into service, ensuring that the erosion-resistant properties are established before any wear or corrosion can occur
Solution Approach 2:
The patent employs a composite coating structure where the anodized aluminum oxide layer provides adhesion and corrosion resistance, while the outer sealant layer provides erosion resistance. This composite approach combines the advantages of both materials to achieve superior overall performance without significantly increasing manufacturing complexity
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
The PEO process creates a hard, dense oxide layer that significantly improves wear resistance and corrosion protection, allowing the coated components to withstand acidic and alkaline conditions and survive multiple erosion tests, outperforming conventional anodization.
Implementation Method 1
A voltage is applied between the first electrode and the second electrode to the electrochemical cell. An aluminum oxide layer is formed on the aluminum containing component.
Implementation Method 2
A plasma electrolytic oxidation (PEO) process is used to form a thick, crystalline aluminum oxide layer on aluminum components
Implementation Method 3
The aluminum oxide layer is then protected by a hexavalent chromate seal. Chromate conversion coatings are formed by dipping the aluminum part that has been anodized in chromic acid
Data Source
AI summary
An aluminum containing component comprises an aluminum alloy and an aluminum oxide layer disposed on the aluminum alloy. The aluminum oxide layer comprises crystalline aluminum oxide. The aluminum containing component is at least one of vane, a fan blade or a fan casing of a low pressure compressor section of a gas turbine. In an embodiment, a method comprises disposing an aluminum containing component in an electrochemical cell that comprises a dilute alkaline solution. The aluminum containing component is electrically contacted to become a first electrode in the electrochemical cell. The wall of the bath is electrically contacted to act as a second electrode in the electrochemical cell. A voltage is applied between the first electrode and the second electrode to form an aluminum oxide layer on the aluminum containing component.