Composite Environmental Barrier Coating With Dual-Zone Creep Control
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Solution Overview
Problem
Composite materials used in turbomachinery are prone to damage from thermal and oxidative environments, leading to reduced lifespan due to surface cracking and deep cracking in the protective layers.
Innovation Solution
A protective coating with distinct zones: an outer zone containing a grain growth inhibitor to control creep and prevent surface cracking, and an inner zone to maintain creep for stress relief, using rare earth silicates and grain growth inhibitors like zirconium oxide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the protective coating is made with conventional environmental barrier materials, then the coating provides thermal and environmental protection, but surface cracking occurs due to significant creep in the outer layer under thermal gradients
Solution Approach 1:
The coating is divided into two zones with different compositions and creep characteristics: an outer zone with low creep (adding Al2O3, Y2O3, or ZrO2 to rare earth disilicate) to prevent surface cracking, and an inner zone with conventional creep behavior to maintain stress relief. This local differentiation allows each zone to perform its specific function optimally.
Solution Approach 2:
The outer zone uses a composite material system combining rare earth disilicate with oxide additives (Al2O3, Y2O3, or ZrO2) to achieve controlled low creep behavior. This composite approach modifies the creep characteristics of the conventional rare earth disilicate while maintaining its environmental barrier properties.
2Strength
If the coating material is made creep-resistant to prevent surface cracking, then surface integrity is improved, but deep cracking may occur at the interface between the bonding layer and coating due to inability to relieve oxidation-induced stresses
Solution Approach 1:
The coating is divided into two zones with different compositions and creep characteristics: an outer zone with low creep (adding Al2O3, Y2O3, or ZrO2 to rare earth disilicate) to prevent surface cracking, and an inner zone with conventional creep behavior to maintain stress relief. This local differentiation allows each zone to perform its specific function optimally.
3Device complexity
If a single-zone protective coating is used, then the coating structure is simple, but it cannot simultaneously prevent both surface cracking and deep cracking under operating conditions
Solution Approach 1:
The protective coating is segmented into two distinct zones: an outer zone with modified composition for low creep and an inner zone with conventional composition for stress relief. This segmentation allows the coating to address both surface cracking and deep cracking issues that cannot be solved with a single homogeneous material.
Solution Approach 2:
The coating is divided into two zones with different compositions and creep characteristics: an outer zone with low creep (adding Al2O3, Y2O3, or ZrO2 to rare earth disilicate) to prevent surface cracking, and an inner zone with conventional creep behavior to maintain stress relief. This local differentiation allows each zone to perform its specific function optimally.
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 coating significantly reduces surface cracking and prevents deep cracking, extending the lifespan of composite material parts under high-temperature and oxidative conditions.
Implementation Method 1
said first zone comprising at least one grain growth blocking agent in a sufficient content to obtain this first creep
Implementation Method 2
having a first creep in operation exhibiting a deformation less than or equal to 0.07% when subjected to a compressive stress of at least 50 MPa for a period of 10 hours at a temperature between 1050°C and 1300°C
Implementation Method 3
having a second creep in operation exhibiting a deformation of at least 0.01% when subjected to a compressive stress of at least 50 MPa for a period of 10 hours at a temperature between 900°C and 1000°C
Implementation Method 4
coating creep at the point where this second mode of damage would normally occur allows these local stresses to be relieved
Implementation Method 5
an environmental barrier which is itself coated with an abradable layer
Implementation Method 6
a thermal shield coating layer on a substrate made of a ceramic fiber-reinforced ceramic matrix composite
Data Source
Figure 1~2
AI summary
The invention relates to a part made of coated composite material, comprising: - a substrate made of composite material having a ceramic matrix; - a tie-coat layer covering the substrate; and - a protective coating that is on the tie-coat layer and that defines at least one environmental barrier, the protective coating comprising at least one rare-earth silicate and comprising at least: - a first outer region comprising an outer surface of the protective coating opposite to the substrate and having a first working creep, having deformation of less than or equal to 0.07% when a compressive stress of at least 50 MPa is applied for a duration of 10 hours at a temperature of between 1050°C and 1300°C, said first region comprising at least one grain growth inhibitor in a sufficient quantity to obtain this first creep; and - a second, inner, environmental barrier region, comprising at least one interface of the protective coating with the tie-coat layer and having a second working creep, having deformation of at least 0.01% when a compressive stress of at least 50 MPa is applied for a duration of 10 hours at a temperature of between 900°C and 1000°C.