Composite Mould Tool Cold-Spray Sealing for Vacuum Integrity
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Solution Overview
Problem
Composite mould tools, particularly hard tooling mould tools, often suffer from lack of vacuum integrity, which is only apparent after manufacturing or during use, and conventional repair methods like welding are costly, complex, and may introduce distortion.
Innovation Solution
A method involving cold spraying a hermetically sealing layer on the reverse face of the mould tool precursor using particles of a second metal with similar thermal expansion coefficients to the first metal, followed by subtractive manufacturing of the faceplate, to ensure vacuum integrity and prevent distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional repair methods like welding are used on composite mould tools, then structural weaknesses can be repaired, but the tools may experience distortion and the repair process becomes costly and complex
Solution Approach 1:
The patent replaces welding (a thermal/mechanical process) with cold gas dynamic spraying (a kinetic deposition process). The spraying process uses supersonic gas flow to accelerate metal particles onto the substrate, creating a hermetic seal without the heat-affected zone and distortion associated with welding. This substitution resolves the contradiction by maintaining repair effectiveness while eliminating complexity and distortion issues.
Solution Approach 2:
The patent changes the fundamental parameters of the repair process: instead of using high temperature and pressure (welding), it uses low temperature and high velocity particle impact (cold spraying). The coating material is applied in a cold state and bonds through plastic deformation upon impact, fundamentally altering the repair mechanism to avoid distortion while maintaining structural integrity and vacuum sealing.
2Reliability
If welding is used to repair composite mould tools, then structural weaknesses can be addressed, but the process becomes costly and time-consuming
Solution Approach 1:
The replacement of welding with cold gas dynamic spraying fundamentally changes the repair approach from a multi-step thermal process to a direct deposition process. The spraying operation can be performed quickly without the need for preheating, prolonged heating cycles, or extensive post-weld heat treatment, significantly reducing repair time while maintaining effectiveness.
3Reliability
If a hermetic seal is applied to the reverse face, then vacuum integrity is maintained, but thermal expansion mismatch may cause distortion
Solution Approach 1:
The patent applies the homogeneity principle by selecting a coating material (Fe-Ni alloy) that is compositionally similar to the substrate material (Invar alloy). Both materials have comparable nickel content (36-42% Ni in substrate, 30-40% Ni in coating) and similar coefficients of thermal expansion. This material homogeneity ensures uniform thermal expansion behavior throughout the tool, preventing distortion while maintaining the hermetic seal.
Solution Approach 2:
The patent directly addresses thermal expansion by carefully matching the coefficient of thermal expansion between the coating material and the substrate. By selecting a Fe-Ni alloy coating with thermal expansion properties similar to the Invar substrate, the patent ensures that both layers expand and contract at similar rates during thermal cycling, preventing stress buildup and distortion that would occur with mismatched materials.
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 method effectively seals the mould tool, maintaining vacuum integrity and extending its longevity without distortion, making it suitable for high-value, large aerospace components.
Implementation Method 1
hermetically sealing the precursor by cold spraying a layer on the second face using particles comprising a second metal
Implementation Method 2
hermetically sealing the precursor by cold spraying a layer on the second face
Data Source
AI summary
A method of manufacturing, at least in part, a composite mould tool is described. At S101, the method comprises obtaining a mould tool precursor having a first face and a reverse second face, wherein the precursor comprises a first metal. At S102, the method comprises hermetically scaling the precursor by cold spraying a layer on the second face using particles comprising a second metal, wherein the respective coefficients of thermal expansion of the first metal and the second metal are within a factor of 5. At S103, the method comprises providing a faceplate of the composite mould tool by subtractive manufacturing of the first face.