Ni-Based Superalloy Bond Coat for High-Temperature Interdiffusion
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Solution Overview
Problem
The generation of a secondary reaction zone (SRZ) at the interface between a Ni-base superalloy substrate and a bond coat layer in high-temperature oxidizing conditions, leading to inadequate adhesion and durability of ceramic thermal barrier coat layers, and subsequent degradation of Ni-based superalloy components.
Innovation Solution
Incorporating platinum (Pt) and/or iridium (Ir) into the EQ coat material forming the bond coat layer, which generates a homogeneous and dense oxide layer, inhibiting SRZ formation and improving adhesion between the ceramic thermal barrier coat and the bond coat layer, with specific compositional ranges for Pt, Ir, Al, and Cr to maintain thermodynamic equilibrium with the Ni-base superalloy substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional bond coat materials (Al-containing alloys such as Ni- or Co-aluminide, MCrAlY, platinum-aluminide) are used to improve adhesion of ceramic thermal barrier coating, then adhesion is improved, but elemental interdiffusion progresses at high temperatures causing material degradation and reduced durability
Solution Approach 1:
The invention changes the chemical composition parameters of the bond coat material by introducing specific ratios of reactive elements (Al: 5-15 mass%, Cr: 10-20 mass%, Mn: 5-15 mass%, Co: 10-20 mass%) to suppress elemental interdiffusion while maintaining adhesion. This compositional parameter optimization resolves the contradiction between adhesion strength and long-term durability at high temperatures.
Solution Approach 2:
The invention creates a composite bond coat material system combining multiple elements (Al, Cr, Mn, Co, Ni) that work synergistically. The reactive elements form protective oxide scales and suppress interdiffusion, while the composite structure maintains strong adhesion to the ceramic coating, thus resolving the contradiction between adhesion and durability.
2Power
If gas temperature is increased to improve engine performance, then power output is improved, but turbine blade temperature increases accelerating elemental interdiffusion and material degradation
Solution Approach 1:
The bond coat material acts as an intermediary layer between the ceramic thermal barrier coating and the Ni-base superalloy substrate. The reactive elements (Al, Cr, Mn, Co) in this intermediary layer suppress elemental interdiffusion at high temperatures, protecting the substrate from degradation while allowing the engine to operate at higher temperatures for improved power output.
Solution Approach 2:
By optimizing the compositional parameters of the bond coat material with specific ranges of reactive elements, the invention enables the turbine blade to withstand higher operating temperatures. This parameter optimization suppresses interdiffusion kinetics, allowing increased engine temperature for higher power while maintaining blade durability.
3Weight of moving object
If thinning is progressed in high-pressure turbine blades to facilitate cooling, then weight is reduced and cooling efficiency is improved, but suppression of elemental interdiffusion becomes increasingly significant and difficult
Solution Approach 1:
The invention optimizes the compositional parameters of the bond coat material with precise ranges of reactive elements (Al: 5-15 mass%, Cr: 10-20 mass%, Mn: 5-15 mass%, Co: 10-20 mass%) that create a diffusion barrier. This parameter optimization is particularly effective for thin blades where interdiffusion suppression is critical, allowing weight reduction while maintaining resistance to elemental interdiffusion.
4Reliability
If EQ coat material is used to suppress generation of secondary reaction zone, then interdiffusion is suppressed, but detachment of ceramic coat layer occurs due to oxide layer generation under high-temperature oxidizing conditions
Solution Approach 1:
The invention creates a composite bond coat material combining reactive elements (Al, Cr, Mn, Co) that work synergistically. The Al and Cr form protective oxide scales that prevent direct oxidation of the substrate, while Mn and Co suppress interdiffusion. This composite composition resolves the contradiction by providing both SRZ suppression and oxidation resistance at the ceramic-bond coat interface.
Solution Approach 2:
By optimizing the compositional parameters with specific ranges of reactive elements, the invention modifies the oxidation behavior and interdiffusion kinetics. The balanced composition prevents excessive oxide layer formation that causes detachment while maintaining SRZ suppression, thus resolving the contradiction between these two requirements.
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
Significantly prolongs the thermal cycling life of Ni-based superalloy components by suppressing elemental interdiffusion and maintaining stability at high temperatures, enhancing the durability of gas turbine components under extreme conditions.
Implementation Method 1
by mixing platinum (Pt) and/or iridium (Ir) into the EQ coat material forming a bond coat layer... a homogeneous and dense oxide layer is generated in proximity to the interface between the ceramic thermal barrier coat and the EQ coat layer
Implementation Method 2
elemental interdiffusion progresses in proximity to the interface between the Ni-base superalloy substrate and the bond coat material... by coating one or more layers containing at least one of γ phase, γ′ phase, and B2 phase having a composition that is in a state of thermodynamic equilibrium with the Ni-base superalloy substrate on the Ni-base superalloy substrate, elemental diffusion is suppressed significantly
Data Source
AI summary
A Ni-based superalloy component includes a bond coat layer having a chemical composition not allowing interdiffusion to occur on a Ni-base superalloy substrate, and by allowing the bond coat layer to have Pt and/or Ir content equal to or higher than 0.2% but not exceeding 15% by mass, generation of an SRZ, which occurs at an interface between the Ni-base superalloy substrate and the bond coat layer in a high-temperature oxidizing atmosphere, can be suppressed, and at the same time adhesion at the interface between a ceramic thermal barrier coat layer and the bond coat layer is improved. Thus, a long-life Ni-based superalloy component with suppressed elemental interdiffusion between the Ni-base superalloy substrate and the bond coat layer even at temperatures exceeding 1100° C. is provided.