Vapor Phase Aluminization of Turbomachine Cavity Coatings
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Solution Overview
Problem
The existing vapor phase aluminization method for depositing a protective coating on hollow metal parts with cavities fails to achieve uniform thickness within the cavities, leading to reduced protection and cooling efficiency due to the inability of carrier gases and active components to access narrow passageways effectively.
Innovation Solution
A method where a metal donor pellet, composed of aluminum and other metals like Cr, Ni, Co, or Fe, is placed inside the cavity through the cooling fluid inlet, allowing for improved accessibility and uniform deposition of the aluminum coating within the cavity, using a carrier gas like argon to transport the halide and react with the metal substrate, eliminating the need for organic binders and simplifying the process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the vapor phase aluminization method is applied to hollow metal parts with cavities, then the protective coating can be deposited on accessible surfaces, but the coating thickness becomes non-uniform and insufficient inside narrow passageways
Solution Approach 1:
The donor is segmented into multiple small pellets distributed throughout the cavity rather than using a single large donor. This segmentation allows the aluminum vapor to be generated at multiple locations within the cavity, ensuring uniform coating thickness on all internal surfaces including narrow passageways that would be inaccessible from a single donor location.
Solution Approach 2:
The carrier gas acts as an intermediary to transport aluminum vapor from the donor pellets to the cavity surfaces. The gas flow pattern is designed to penetrate deep into narrow passageways, delivering aluminum vapor to areas that would otherwise be inaccessible, thereby achieving uniform coating thickness throughout the entire cavity.
2Ease of manufacture
If traditional donor forms (blocks or granules) are used, then the aluminization process can proceed, but the donor is difficult to insert and remove from narrow cavities
Solution Approach 1:
The donor is divided into multiple small pellets that can be easily inserted through narrow openings into the cavity. These small pellets are simple enough to pass through restricted access areas but can collectively provide sufficient aluminum material for complete cavity coating when distributed properly throughout the space.
Solution Approach 2:
The donor pellets are designed as disposable elements that are inserted into the cavity, perform their function of providing aluminum vapor for coating, and are then removed. They do not need to be reused, which simplifies their design to focus solely on ease of insertion and effective vapor generation during the aluminization process.
3Quantity of substance
If the cavity is completely filled with donor material, then sufficient aluminum is available for coating, but the part cannot be accessed or assembled
Solution Approach 1:
Instead of uniformly filling the entire cavity with donor material, the aluminum pellets are strategically distributed at specific locations within the cavity where they can effectively contribute to coating formation. This localized distribution provides sufficient aluminum vapor for complete cavity coating while maintaining clear pathways for assembly and inspection operations.
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 approach ensures a uniform and sufficient thickness of the aluminum coating on the inner cavity walls, enhancing protection against high-temperature oxidation and maintaining cooling efficiency without leaving residues that require specific cleaning, and allows for easier manipulation and machining of the pellet for precise fitting.
Implementation Method 1
At the reaction temperature, between 900° C. and 1150° C., the halide decomposes on the surface of the part into gaseous halogen and aluminum which diffuses into the metal.
Implementation Method 2
the halide then decomposes on contact with the metal substrate to be coated allowing the aluminum to be deposited
Implementation Method 3
aluminum which diffuses into the metal
Implementation Method 4
The inert gas is made to travel over the activator at a temperature allowing the sublimation of the halogen which is carried to the donor
Data Source
AI summary
A method of aluminization by deposit in the vapor phase for protection against oxidation at high temperature of a metal part of a turbomachine. The part includes a cavity with an opening that can be accessed from the outside. A halide is formed by reaction between a halogen and a metal donor containing aluminum, then the halide is transported by a carrier gas to come into contact with the metal part, the metal donor being placed at least partly in the cavity. The metal donor is in the form of a pellet obtained by hot sintering under pressure of a mixture of metal powder.