Ceramic Coating Edge Recesses to Reduce Turbine Spallation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Delamination or spalling of thermal barrier coatings from their underlying substrates in gas turbine engines due to differential thermal expansion and contamination, such as CMAS attack, which reduces the coating's ability to accommodate thermal deformations.
Innovation Solution
The implementation of an array of recesses on the substrate, extending to and modified along the edges of the coated region, with beveled surfaces and corresponding recesses in the ceramic coating, to create faults that act as expansion joints and reduce stress concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a continuous ceramic coating is applied on the substrate, then the coating provides complete thermal barrier protection, but the coating is prone to delamination and spalling at edges due to stress concentration from differential thermal expansion
Solution Approach 1:
The continuous coating is segmented by creating an array of recesses in the substrate that extend to and modify the edges of the coated region. These recesses create discontinuities in the coating structure, forming isolated coating segments that can independently accommodate thermal expansion and contraction, thereby reducing stress concentration and preventing edge spallation
Solution Approach 2:
The edge regions of the coating are given different properties from the bulk coating through the recess modification. The recesses create localized stress relief zones at the edges where the coating thickness and structure are altered, providing local adaptability to thermal deformations while maintaining the protective function of the overall coating system
2Temperature
If the coating is made more continuous and uniform, then the thermal barrier performance is improved, but the coating becomes less tolerant to thermally induced sintering shrinkage
Solution Approach 1:
The coating is divided into segmented regions by the recesses, which act as expansion joints. These segments can independently shrink during sintering without generating excessive stress, while still maintaining adequate thermal barrier performance through the collective effect of all coating segments
3Ease of manufacture
If the coating edge is left sharp and perpendicular to the substrate, then the manufacturing process is simpler, but the edge becomes a stress concentration point that accelerates spallation
Solution Approach 1:
The substrate is pre-prepared with an array of recesses before the ceramic coating is applied. This preliminary action creates the stress-relief geometry in advance, allowing the coating to be applied as a relatively simple continuous layer that will naturally form the segmented structure with reduced edge stress during the coating process itself
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 effectively reduces spallation at coating edges and improves tolerance to thermally induced sintering shrinkage, enhancing the durability and performance of ceramic coatings in high-temperature environments.
Implementation Method 1
differential thermal expansion/contraction of the coating and the underlying substrate
Implementation Method 2
create faults that act as expansion joints and reduce stress concentrations
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An article (76) has a body (80) having a first face (124), and a first bevel surface (170) extending from the first face (124). A plurality of first channels (200) along the first bevel surface (170) extend from the first face (124). A ceramic coating (120) is along the first face (124) and the first bevel surface (170).