Turbine Blade Diffusion Barrier Layer Design
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Solution Overview
Problem
Industrial gas turbine blades face challenges with thermal barrier coatings due to Al diffusion from bond coats, leading to reduced substrate strength and oxidation resistance, especially in large blades where precision casting and thermal spray processes can damage diffusion barrier layers, making them brittle and ineffective over long service periods.
Innovation Solution
A turbine blade with a substrate made of a single-crystal alloy containing specific elements, including Re, Cr, and Ni, featuring a σ-phase intermetallic diffusion barrier layer, a metal layer, and a MCrAlY bond coat, stacked in order, which are deposited using thermal spray processes to maintain the diffusion barrier's function without brittleness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a thermal barrier coating with bond coat is applied to increase combustion gas temperature and improve efficiency, then the thermal barrier function is improved, but Al diffusion from bond coat to substrate occurs causing reduced substrate strength
Solution Approach 1:
A diffusion barrier layer comprising Re, Cr, and Ni is introduced as an intermediary between the bond coat and substrate. This layer prevents Al diffusion from the bond coat to the substrate while maintaining the thermal barrier coating's protective function, thereby preserving substrate strength during high-temperature service
2Reliability
If the diffusion barrier layer is made of alloy containing Ru or Re to suppress element diffusion, then diffusion resistance is improved, but the alloy layer decomposes at high temperature and fails to maintain diffusion barrier function
Solution Approach 1:
The composition parameters of the diffusion barrier layer are optimized by specifying Re content at 1.2-1.6%, Cr at 6.9-7.3%, and Ni as balance. This specific compositional range ensures thermodynamic stability as an equilibrium phase while maintaining effective diffusion barrier function at high temperatures throughout the service life
3Productivity
If thermal spray process is used to deposit coating on large turbine blades, then manufacturing efficiency is improved, but the diffusion barrier layer becomes brittle and is damaged during blasting and coating formation
Solution Approach 1:
The diffusion barrier layer is designed as a composite material containing Re, Cr, and Ni in specific proportions. This composite structure provides both brittleness resistance to withstand blasting and thermal spray processes, and maintains diffusion barrier functionality throughout the coating formation process
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 solution provides a long-life turbine blade with a thermal barrier coating that maintains diffusion barrier functionality, preventing substrate strength reduction and oxidation resistance degradation, even under high temperatures and large blade dimensions, enhancing the efficiency and longevity of industrial gas turbines.
Implementation Method 1
Al may diffuse from the bond coat to the substrate during high temperature service, causing formation of a secondary reaction zone (SRZ) in the substrate which may reduce strength of the substrate
Implementation Method 2
The TBC includes a top coat as a thermal barrier formed of an oxide having a low coefficient of thermal conductivity
Implementation Method 3
the diffusion barrier layer, the metal layer, the bond coat and the top coat are stacked in this order on a surface of the blade substrate
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A turbine blade for industrial gas turbine is used which includes a blade substrate formed of a single-crystal heat-resistant alloy containing C: 0.06 to 0.08%, B: 0.016 to 0.035%, Hf: 0.2 to 0.3%, Cr: 6.9 to 7.3%, Mo: 0.7 to 1.0%, W: 7.0 to 9.0%, Re: 1.2 to 1.6%, Ta: 8.5 to 9.5%, Nb: 0.6 to 1.0%, Al: 4.9 to 5.2%, Co: 0.8 to 1.2%, and the remainder substantially consisting of Ni with reference to mass, and includes a diffusion barrier layer, a metal layer, a bond coat, and a top coat, these layers and coats being stacked in this order on a surface of the blade substrate, the metal layer having a thickness of 5 to 30 µm. Thus, the turbine blade can be provided which has a thermal barrier coating formed without loss of a function of the diffusion barrier layer.