Environmental Barrier Coating Backside Heating Control
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Solution Overview
Problem
Ceramic or ceramic matrix composite materials used in high-temperature mechanical systems, such as gas turbine engines, can react with water vapor, leading to material recession and reduced mechanical properties due to the amorphous nature of environmental barrier coatings (EBCs) which become unstable and lose adhesion at high temperatures.
Innovation Solution
A method involving backside heating of a substrate within a furnace enclosure to control the surface temperature of the frontside during thermal spray deposition of EBCs, increasing the crystalline phase content and reducing porosity, thereby enhancing adhesion and stability of the coatings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the substrate is heated to high temperature during thermal spray deposition of EBC, then the crystalline phase content increases and porosity decreases, but the adhesion of the coating deteriorates due to thermal expansion mismatch and coating instability
Solution Approach 1:
The heating process is segmented into two distinct stages: pre-heating the substrate to a controlled temperature (e.g., 500-800°C) before coating deposition, and then post-heating the coated substrate to higher temperatures (e.g., 1000-1400°C) to promote crystalline phase formation. This temporal segmentation allows the coating to be deposited on a moderately heated substrate (improving adhesion) and then crystallized in a separate high-temperature stage (improving stability).
Solution Approach 2:
The substrate is pre-heated to a moderate temperature before EBC deposition to reduce porosity and improve coating adherence during the spraying process, while the full high-temperature treatment is reserved for post-deposition heat treatment to develop the crystalline phase without compromising adhesion. This preliminary action prepares the substrate optimally for coating application.
2Productivity
If the substrate is not heated during thermal spray deposition, then the coating deposition process is simpler and faster, but the porosity of the coating increases and adhesion deteriorates
Solution Approach 1:
The thermal treatment is segmented into pre-heating (moderate temperature during deposition) and post-heating (high temperature after deposition). The pre-heating stage is optimized for coating deposition efficiency with reduced porosity, while the post-heating stage optimizes adhesion and crystalline phase formation, thus maintaining productivity while improving reliability.
Solution Approach 2:
The substrate temperature parameter is dynamically adjusted: maintained at a moderate level (500-800°C) during the thermal spray deposition process to ensure good adhesion and controlled porosity, then increased to high temperatures (1000-1400°C) during post-deposition heat treatment to develop the desired crystalline phase structure and enhance overall coating performance.
3Stability of the object's composition
If the entire thermal spray device is located within a high temperature furnace, then the coating achieves high crystalline phase content, but the device complexity and manufacturing cost increase
Solution Approach 1:
The thermal processing is segmented into two separate operations: (1) thermal spray deposition performed at moderate substrate temperature (achieved through selective pre-heating or controlled environment), and (2) separate post-deposition heat treatment in a furnace to achieve high crystalline phase content. This segmentation allows the use of simpler, more cost-effective equipment for each stage rather than requiring a complex integrated high-temperature spray system.
Solution Approach 2:
The substrate or coating is preliminarily prepared at moderate temperatures during deposition, then subjected to a subsequent high-temperature heat treatment to develop the crystalline phase. This preliminary action at lower temperature simplifies the deposition equipment requirements while achieving the desired high crystalline phase content through the follow-up heat treatment.
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 approach results in improved adhesion and reduced internal stresses in EBCs, extending the lifespan of components by maintaining the crystalline phase and minimizing porosity, thus protecting against water vapor and other deleterious reactions.
Implementation Method 1
heating of the backside of the substrate with the furnace enclosure heats the frontside of the substrate to a surface temperature by heat conduction from the backside of the substrate to the frontside of the substrate
Implementation Method 2
depositing an environmental barrier coating (EBC) on the frontside of the substrate via a thermal spray device
Implementation Method 3
the surface temperature of the frontside of the substrate is selected to control at least one of a porosity of the deposited EBC or a weight percent of a crystalline phase in the deposited EBC
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
Method for forming an environmental barrier coating (EBC) (68) on a substrate (24) including heating (52) a backside (40) of the substrate (24) using a furnace enclosure (14), wherein a frontside (42) of the substrate (24) is outside the furnace enclosure (14), wherein the heating of the backside (40) of the substrate (24) with the furnace enclosure (14) heats the frontside (42) of the substrate (24) to a surface temperature by heat conduction from the backside (40) of the substrate (24) to the frontside (42) of the substrate (24); and depositing (54) the environmental barrier coating (EBC) (68) on the frontside (42) of the substrate (24) via a thermal spray device (22) while the backside (40) of the substrate (24) is heated using the furnace enclosure (14), wherein the surface temperature of the frontside (42) of the substrate (24) is selected to control at least one of a porosity of the deposited EBC (68) or a weight percent of a crystalline phase in the deposited EBC (68).