Plasma Sintering of YSZ Thermal Barrier Coatings
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Solution Overview
Problem
Thermal barriers with YSZ ceramic layers and transverse microcracks in aeronautical and land-based turbines face challenges with erosion and micro-flaking due to hot gas exposure, leading to reduced insulation thickness and shortened part lifespan.
Innovation Solution
A method involving a sintering post-treatment using a plasma torch to control temperature and torch parameters, ensuring the ceramic layer reaches 1300°C to 1700°C for a few seconds, promotes microcracking and enhances erosion resistance without significantly altering production time or cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ceramic layer is sintered at high temperature for extended time, then erosion resistance is improved, but production time increases significantly
Solution Approach 1:
The ceramic layer is pre-sintered during the thermal spray deposition process itself, creating a partially sintered structure that requires less additional sintering time. The plasma spray process naturally provides thermal energy that initiates sintering before the dedicated post-treatment step, thereby reducing the total time required to achieve the desired erosion resistance.
Solution Approach 2:
The invention optimizes the sintering temperature window (1300°C to 1700°C) and controls the thermal exposure duration (5-20 seconds) to achieve maximum erosion resistance with minimal time investment. By precisely controlling these parameters during plasma spray and post-treatment, the process achieves efficient sintering that balances material consolidation with production speed requirements.
2Reliability
If the ceramic layer is sintered to improve erosion resistance, then micro-flaking resistance is improved, but the risk of melting and losing microcrack structure increases
Solution Approach 1:
The invention precisely controls the sintering temperature range (1300°C to 1700°C) to achieve optimal consolidation that improves micro-flaking resistance while preserving the transverse microcrack architecture. This temperature window is carefully selected to provide sufficient thermal energy for particle bonding without exceeding the threshold that would cause complete melting and loss of the microcracked structure.
Solution Approach 2:
The thermal treatment is applied in controlled periodic cycles during plasma spray deposition and post-treatment, allowing the ceramic layer to undergo repeated heating and cooling cycles. This periodic thermal action promotes gradual sintering and microcrack formation while preventing excessive heat accumulation that would lead to melting and structural degradation.
3Adaptability or versatility
If transverse microcracks are introduced to improve thermal cycling resistance, then flexibility is improved, but erosion resistance deteriorates
Solution Approach 1:
The invention creates a heterogeneous microstructure where transverse microcracks are distributed throughout the ceramic layer to provide flexibility and thermal cycling resistance, while the plasma spray process and controlled sintering create locally dense regions that maintain erosion resistance. The microcracks are strategically positioned to accommodate thermal expansion without creating continuous pathways for erosion.
Solution Approach 2:
The thermal barrier coating is structured as a composite system with transverse microcracks providing thermal cycling accommodation and the plasma-sprayed ceramic matrix providing erosion resistance. The combination of microcracked architecture with properly sintered ceramic material creates a composite structure that simultaneously achieves both thermal flexibility and erosion durability.
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 significantly improves the erosion resistance and micro-flaking resistance of thermal barriers, maintaining temperature resistance and reducing maintenance and costs associated with frequent restoration.
Implementation Method 1
Sintering is understood here and throughout this text to mean a consolidation treatment of a material (for example a powder), obtained by minimizing the energy of the system thanks to an energy input (thermal, mechanical, with a laser, a plasma torch, etc.) but without melting at least one of the constituents.
Implementation Method 2
During such a sintering post-treatment, the temperature of the beam spot on the surface of the ceramic layer C (C) is continuously measured and the torch parameters are controlled according to this measurement. The surface of the part opposite the ceramic layer C (C) is cooled to be maintained at a temperature generally below 950°C.
Data Source
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AI summary
A YSZ-type ceramic layer is deposited on a tie sublayer by thermal spraying using a plasma arc torch, said tie sublayer being itself deposited on the part to be protected. A sintering post treatment is carried out by means of a sweep of the ceramic layer by the beam of the plasma arc torch, the temperature at the point of impact of the beam at the surface of the ceramic layer (C) being, during this sweep, between 1300°C and 1700°C.