Non-destructive CMAS Infiltration Characterization of Thermal Barrier Coatings
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Solution Overview
Problem
Current methods for characterizing CMAS infiltration in thermal barrier coatings (TBCs) are destructive, making it impossible to non-invasively determine the infiltration depth and assess the lifetime of coatings, which is critical for maintaining the protective function of turbine blades and other high-temperature components.
Innovation Solution
The use of Raman Spectroscopy, specifically 3D Raman mapping, to analyze the phase changes in TBCs caused by CMAS infiltration, allowing for non-destructive characterization of the infiltration depth and damage assessment by correlating phase changes with CMAS interaction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If destructive metallographic cross-section preparation is used to measure CMAS infiltration depth, then measurement precision is improved, but the component is damaged and cannot be reused
Solution Approach 1:
The patent replaces the mechanical destructive cross-section preparation method with Raman spectroscopy, an optical/non-contact measurement technique. This substitution allows measurement of CMAS infiltration depth without physically destroying the coating, thereby maintaining component reusability while achieving the required measurement precision through spectral analysis of phase changes in the coating material
Solution Approach 2:
The patent introduces Raman spectroscopy as an intermediary measurement method that indirectly detects CMAS infiltration depth by measuring phase changes in the coating material (e.g., tetragonal to monoclinic phase transition in zirconia). This intermediary approach avoids direct physical contact and destruction of the coating, enabling non-destructive measurement with sufficient precision
2Reliability
If existing non-destructive TGO stress measurement methods are used, then component integrity is maintained, but the ability to measure CMAS infiltration depth is lost due to inability to mitigate CMAS signal contribution
Solution Approach 1:
The patent applies local quality analysis by examining Raman spectra at different depths and locations within the coating to identify specific spectral signatures associated with CMAS infiltration. By analyzing local variations in phase composition (e.g., monoclinic phase concentration) at different depths, the method can distinguish CMAS-related signals from other coating features, enabling precise infiltration depth measurement while maintaining component integrity
Solution Approach 2:
The patent transitions from conventional 2D surface or cross-sectional analysis to 3D depth-resolved Raman mapping. By introducing the depth dimension through confocal Raman microscopy or depth-profiling techniques, the method can selectively probe different depths within the coating and isolate CMAS infiltration signals from the overall coating response, achieving both non-destructive measurement and precise infiltration depth determination
3Reliability
If Raman mapping is used to analyze phase changes in TBCs, then non-destructive characterization is achieved, but measurement complexity increases
Solution Approach 1:
The patent segments the complex Raman mapping measurement process into manageable components: (1) acquiring Raman spectra at discrete depth points or locations, (2) identifying characteristic spectral peaks for different phases (tetragonal, monoclinic, CMAS), and (3) processing the spectral data to extract infiltration depth information. This segmentation simplifies the overall complexity by breaking down the 3D mapping into sequential 1D or 2D measurements that can be processed independently
Data Source
AI summary
The present invention provides a non-destructive method of characterizing CMAS infiltration and CMAS assisted damage in thermal barrier coatings (TBCs). Such approach is especially relevant for determining the lifetime of coatings on e.g. turbines or parts of the turbines such as blades or in-liners of the combustion chambers. The turbines can be gas turbines or high-pressure turbines or others and may be stationary or used for example in aviation.