Unfixed Mounting Member for Thermal Warping in Coating Chambers
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Solution Overview
Problem
Conventional coating chambers for aerospace components warp due to thermal expansion and contraction, leading to uneven coating distribution and leakage, which reduces the yield of acceptably coated turbine airfoils and necessitates frequent replacements.
Innovation Solution
A coating apparatus design featuring a mounting member that is unfixed or partially secured to the chamber wall, allowing for independent thermal expansion and contraction, and a gas tube with perforations for uniform gas flow, preventing warping and ensuring consistent coating distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the mounting member is fixed rigidly to the chamber wall, then the structural stability is improved, but thermal warping occurs due to thermal expansion and contraction during the CVD process
Solution Approach 1:
The mounting member is designed with dynamic characteristics that allow it to expand and contract freely in response to thermal changes during the CVD process. The mounting boss is not rigidly fixed to the chamber wall, enabling thermal movement without generating warping stresses that would compromise coating uniformity.
Solution Approach 2:
The design explicitly accounts for thermal expansion and contraction of the mounting member during heating and cooling cycles. By allowing the mounting boss to move freely rather than constraining it rigidly, the system accommodates thermal dimensional changes without generating harmful stresses, thereby preventing warping and maintaining reliable coating deposition.
2Reliability
If sealing gaskets are added to prevent leakage, then coating chemical leakage is reduced, but the complexity of the mounting system increases and reliability decreases due to gasket failure
Solution Approach 1:
The solution removes the sealing gasket component entirely from the mounting system. By designing the mounting boss with a clearance fit rather than a rigid fixed connection, the system achieves sealing through the interference fit between the airfoil and mounting boss without requiring additional gasket components, thereby reducing complexity and eliminating gasket-related failure modes.
3Shape
If the mounting member is constrained by the chamber wall, then positional stability is improved, but warping occurs due to restricted thermal expansion
Solution Approach 1:
The mounting member transitions from a static rigidly-fixed design to a dynamic design that accommodates thermal movement. The clearance fit allows the mounting boss to move positionally in response to thermal expansion and contraction, maintaining both positional stability during operation and warping resistance through free thermal movement.
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 solution provides a robust coating apparatus that maintains structural integrity during the CVD process, ensuring consistent and even coating distribution on turbine airfoil surfaces, reducing the need for frequent replacements and improving overall coating efficiency.
Implementation Method 1
A gas tube is positioned adjacent to the mounting member in a milled out groove in the mounting member and includes spaced apart perforations that fluidly connect the gas tube and the chamber to a remote gas source
Implementation Method 2
The mounting member is unfixed relative to a chamber wall of the coating chamber. Thus, the chamber wall does not restrict the mounting member during thermal expansion and contraction of the mounting member, avoiding warping
Implementation Method 3
The coatings are typically deposited on the internal surfaces of the internal air passages using a chemical vapor deposition (CVD) process carried out at temperatures on the order of 2000° F. inside a coating chamber
Data Source
AI summary
A coating apparatus includes a mounting member for mounting a turbine airfoil in a coating chamber. The mounting member defines a chamber therein and includes a mounting port that is adapted to receive the turbine airfoil. The mounting port provides a fluid connection between the chamber and an internal passage of the airfoil. A support member is mounted between the chamber wall and mounting member and bears the weight of the mounting member. The mounting member is unfixed relative to a chamber wall of the coating chamber. Thus, the chamber wall does not restrict the mounting member during thermal expansion and contraction of the mounting member and avoids warping of the mounting member.