Dual-Layer Mask for Gas Turbine Chromide Coating Protection
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Solution Overview
Problem
Conventional mask materials used in the aluminizing process of gas turbine components react with and deplete the underlying chromide coating, leading to inadequate protection against type II hot corrosion and accelerated stress-corrosion-cracking failure.
Innovation Solution
A dual-layer mask composition comprising an inner buffer layer of mixed chromium-based powder and inert ceramic powder in a binder solution, and an outer getter layer of nickel-based powder and inert ceramic powder, which prevents aluminide coating deposition and chromium depletion from the pre-existing chromide coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional mask materials are used during the aluminizing process, then the masking function is provided, but the chromide coating is depleted and its integrity is compromised
Solution Approach 1:
The patent introduces a dual-layer mask composition as an intermediary between the chromide coating and the aluminizing process. The inner layer containing chromium-based powder acts as a buffer that prevents direct harmful interaction between conventional mask materials and the chromide coating, thereby preventing chromium depletion while maintaining masking functionality.
Solution Approach 2:
The patent uses a composite dual-layer mask material combining chromium-based powder with inert ceramic powder in the inner layer, and nickel-based powder with inert ceramic powder in the outer layer. This composite structure provides both the necessary masking function and protection against chromium depletion from the chromide coating.
2Reliability
If aluminide coating is deposited onto chromide coating, then oxidation resistance is improved, but corrosion resistance against type II hot corrosion is degraded
Solution Approach 1:
The patent applies preliminary protective action by using the dual-layer mask composition to prevent aluminide coating deposition on the chromide coating before the aluminizing process occurs. The mask composition actively counteracts the potential harmful effect of aluminum spillover onto the chromide coating, preserving the chromide coating's corrosion resistance properties.
3Ease of operation
If conventional mask material reacts with chromide coating, then masking is achieved, but stress-corrosion-cracking resistance is reduced
Solution Approach 1:
The dual-layer mask composition serves as a protective intermediary that prevents direct chemical reaction between conventional mask materials and the chromide coating. The inner layer with chromium-based powder specifically buffers against reactions that would deplete chromium and weaken the coating's stress-corrosion-cracking resistance, while still providing the necessary masking function.
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 dual-layer mask composition effectively maintains the structural integrity and corrosion resistance of the chromide coating by preventing aluminide deposition and chromium depletion, thereby extending the service life and enhancing protection against type II hot corrosion.
Implementation Method 1
said chromium-based powder having a chromium activity equal to or higher than a chromium activity in the pre-existing and underlying chromide coating
Implementation Method 2
an outer getter layer overlying said inner buffer layer consisting essentially of nickel-based powder and an outer inert ceramic powder
Data Source
AI summary
A novel dual layer mask formulation is provided. In particular, the mask has a unique composition that protects the integrity of an underlying chromide coating, prevents chromium depletion from the chromide coating and prevents a subsequent aluminide coating from being deposited thereon.