Discontinuous Diffusion Barrier for Single Crystal Turbine Blades
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Solution Overview
Problem
Conventional diffusion barrier layers in turbine blades for industrial gas turbines suffer from rapid cracking and loss of effectiveness under thermal and mechanical fatigue, leading to reduced durability and lifespan due to continuous layer formation and element diffusion into the substrate.
Innovation Solution
A discontinuous multilayer diffusion barrier layer is formed using a Re-containing alloy with Cr and Ni, deposited through a specific process involving solution heat treatment, shaping, barrier deposition, bond coat application, and top coat deposition, which suppresses element diffusion and enhances durability against thermal and mechanical fatigue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a continuous diffusion barrier layer is formed to prevent element diffusion into the substrate, then oxidation resistance and corrosion resistance are improved, but rapid cracking occurs under thermal and mechanical fatigue leading to reduced durability
Solution Approach 1:
The continuous diffusion barrier layer is divided into multiple discrete layers (first diffusion barrier layer and second diffusion barrier layer) separated by an interlayer. This segmentation prevents crack propagation that would occur in a continuous layer while maintaining the diffusion barrier function through the stacked structure.
2Strength
If a multilayer alloy coating is applied to suppress element diffusion, then mechanical property deterioration is prevented, but the complex deposition process and heat treatment increase manufacturing complexity
Solution Approach 1:
The diffusion barrier function is divided into multiple layers with different compositions and functions. The first diffusion barrier layer (Ni-Re alloy) provides initial barrier function, the interlayer (Ni-Cr-Al alloy) provides oxidation resistance and stress relief, and the second diffusion barrier layer provides additional diffusion protection. This segmented approach maintains strength while managing manufacturing complexity through functional differentiation.
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 discontinuous diffusion barrier layer effectively prevents cracking and maintains structural integrity by reducing diffusion and stress-induced strain, thereby improving the durability and extending the lifespan of turbine blades.
Implementation Method 1
a diffusion barrier layer which is directly in contact with the surface of the single crystal alloy substrate and has a multilayer and discontinuous structure
Implementation Method 2
Oxides of low coefficient of thermal conductivity are used for the top coat, and yttria stabilized zirconia (YSZ), in which the crystalline structure is made stable by addition of yttria is widely used
Implementation Method 3
the bond coat for providing oxidation resistance and corrosion resistance. Because alumina is preferably used for the TGO, the bond coat typically has a higher Al concentration than the substrate
Data Source
Figure 1
Figure 2A~2B
Figure 3~4
AI summary
Disclosed is a turbine blade for an industrial gas turbine including a blade substrate; a multilayer alloy coating containing a diffusion barrier layer; a bond coat; and a top coat, the blade substrate being formed of a single crystal alloy which consists essentially of 0.06 to 0.08% of C, 0.016 to 0.035% of B, 0.2 to 0.3% of Hf, 6.9 to 7.3% of Cr, 0.7 to 1.0% of Mo, 7.0 to 9.0% of W, 1.2 to 1.6% of Re, 8.5 to 9.5% of Ta, 0.6 to 1.0% of Nb, 4.9 to 5.2% of Al, 0.8 to 1.2% of Co, and the balance being Ni and incidental impurities by weight, the multilayer alloy coating, the bond coat and the top coat being directly and sequentially laminated on a surface of the blade substrate, in which the diffusion barrier layer is a multilayer and a discontinuous layer. Thus, the thermal barrier coating structure including a diffusion barrier layer can be provided for the single-crystal turbine blade for the industrial gas turbine formed of a single crystal alloy. The thermal barrier coating structure can suppress growth of a secondary reaction zone caused by element diffusion into the substrate, and can provide durability against thermal fatigue due to thermal cycles and durability against mechanical fatigue.