Ceramic Nanofiber Repair for Gas Turbine Coating Defects
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Gas turbine engine components in the core gaspath face extreme temperatures that can damage ceramic barrier coatings, leading to defects and imperfections, which existing repair methods struggle to effectively address.
Innovation Solution
A repair process involving abrading damaged regions to create a dimple and depositing a patch of networked ceramic nanofibers formed by blow-spinning, which are thermally treated to convert the precursor solution into zirconium oxide filaments, providing a tangled porous network that seals pores and enhances thermal insulation and mechanical interlock.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional barrier coatings are used to protect the substrate from extreme temperatures, then thermal protection is provided, but the coatings become damaged and develop defects under extreme temperature conditions
Solution Approach 1:
The invention uses a porous nanofiber mat made of ceramic fibers with diameters of 1-500 nanometers. The porous structure allows the material to accommodate thermal expansion and stress while maintaining thermal barrier properties. The nanoscale pores and interconnected fiber network provide both thermal insulation and mechanical flexibility, resolving the contradiction between thermal protection and coating integrity under extreme temperatures.
Solution Approach 2:
The invention creates a composite structure by combining the porous nanofiber mat with the existing ceramic barrier coating. The nanofiber mat serves as a reinforcement layer that enhances the coating's resistance to thermal stress and mechanical damage. This composite approach allows the system to maintain both thermal protection and structural reliability under extreme operating conditions.
2Reliability
If the ceramic barrier coating is repaired by conventional methods, then defect coverage is achieved, but the repair lacks mechanical interlock and strain tolerance
Solution Approach 1:
The invention applies the nanofiber mat specifically to damaged regions of the coating rather than the entire surface. The mat is tailored to cover defects such as spalls, cracks, and pinholes while preserving the intact surrounding coating. This localized application provides enhanced mechanical interlock and strain tolerance precisely where needed, without unnecessarily modifying the entire coating surface.
Solution Approach 2:
The nanofiber mat functions as a flexible reinforcement layer that can conform to the contours of the damaged coating surface. The thin, flexible nature of the nanofiber mat allows it to bridge cracks and accommodate thermal expansion differently from rigid conventional repair materials, providing superior mechanical interlock and strain tolerance at the repair site.
3Shape
If the ceramic barrier coating surface is made smooth, then aesthetic appearance is improved, but pore sealing and corrosion resistance are reduced
Solution Approach 1:
The nanofiber mat inherently possesses a porous structure with nanoscale pores that effectively seal larger pores and defects in the underlying coating. The high surface area to volume ratio of the nanofibers creates a dense network that blocks corrosion pathways while maintaining overall surface smoothness. This resolves the contradiction by providing pore sealing without requiring surface roughening.
4Reliability
If a rigid repair patch is applied to the damaged coating, then defect coverage is achieved, but strain tolerance and flexibility are reduced
Solution Approach 1:
The nanofiber mat is inherently flexible due to its nanoscale fiber structure and porous network. This flexibility allows the repair patch to accommodate thermal expansion, contraction, and mechanical strain without cracking or delaminating. The mat can conform to the dynamic stresses experienced by the coating during operation, maintaining defect coverage while providing superior strain tolerance compared to rigid repair 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 repair process effectively seals pores, enhances thermal insulation, and provides mechanical protection by forming a flexible, strain-tolerant patch that integrates with the existing ceramic barrier coating, improving durability and corrosion resistance.
Implementation Method 1
spraying a precursor solution through an inner nozzle while flowing a process gas from an outer concentric nozzle such that the precursor when sprayed elongates into ultra-thin filaments
Implementation Method 2
followed by a thermal treatment to remove the binders and sinter the ceramic to convert the precursor solution to ceramic
Implementation Method 3
thermal treatment to remove the binders and sinter the ceramic
Implementation Method 4
the networked ceramic nanofibers extend into pores of the porous columnar microstructure in the dimple
Implementation Method 5
Gas turbine engine components in the core gaspath may be subject to temperatures in excess of the melting temperature of the component substrate. Cooling features and barrier coatings are used to protect the substrate from these extreme temperatures.
Data Source
Figure 1~2
Figure 3~7
Figure 6
AI summary
A repair process for an article (60) such as an airfoil includes providing an article that has a substrate (68) and a ceramic barrier coating (70) disposed on the substrate (68), where the ceramic barrier coating (70) has a damaged region (72c), abrading the damaged region (72c) to provide a dimple (82) in the ceramic barrier coating (70), wherein a remaining region (84) of the ceramic barrier coating (70) adjacent the dimple (82) remains intact, and depositing a patch (86) of networked ceramic nanofibers (88) in the dimple (82).