MCrAlY Coating Thermal Expansion Mismatch Reduction
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Solution Overview
Problem
Current metallic coatings for high temperature gas turbine engine components face challenges in balancing fatigue resistance and oxidation resistance, with diffused aluminides providing inadequate high temperature protection and MCrAlY coatings suffering from tensile internal stress and thermal expansion mismatch.
Innovation Solution
A low-cost metallic coating composition with specific weight percentages of cobalt, chromium, aluminum, yttrium, hafnium, silicon, zirconium, tantalum, tungsten, molybdenum, and platinum, applied using techniques like cathodic arc plasma vapor deposition, which reduces thermal expansion mismatch and enhances oxidation and fatigue resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If diffused aluminide coatings are used, then fatigue resistance is improved, but high temperature oxidation resistance deteriorates
Solution Approach 1:
The patent uses a composite coating structure with multiple layers: a diffused aluminide base layer providing fatigue resistance, an intermediate MCrAlY layer, and an overlay coating with active elements (yttrium, hafnium, silicon) on top. This composite structure combines the advantages of both coating types while mitigating their individual disadvantages.
Solution Approach 2:
Different regions of the coating have different compositions and functions. The diffused aluminide layer provides fatigue resistance at the substrate interface, the intermediate layer provides transition and oxidation protection, while the overlay layer provides enhanced oxidation resistance at the surface. Each layer is optimized for its specific function.
2Object-affected harmful factors
If overlay MCrAlY coatings are used, then high temperature oxidation resistance is improved, but fatigue resistance deteriorates due to tensile internal stress
Solution Approach 1:
The multi-layer composite structure distributes stress more evenly. The diffused aluminide base layer has compressive stress that counteracts the tensile stress in the overlay layer, reducing net tensile stress and improving fatigue resistance while maintaining oxidation protection.
Solution Approach 2:
The patent modifies the composition and thickness parameters of each layer to optimize stress distribution. By controlling the aluminum content in the diffused layer and the thickness of the intermediate layer, the overall stress state is adjusted to reduce tensile stress while maintaining oxidation resistance.
3Object-affected harmful factors
If refractory metals are added to improve oxidation resistance, then coating performance is improved, but manufacturing cost increases
Solution Approach 1:
Active elements (yttrium, hafnium, silicon) are concentrated in the overlay layer where they are most needed for oxidation resistance, rather than distributing them throughout the entire coating. This localized placement maximizes performance while minimizing material cost.
Solution Approach 2:
The patent uses smaller amounts of expensive refractory elements compared to conventional coatings, replacing some with more cost-effective elements like silicon and aluminum that can provide similar oxidation protection when properly configured in the multi-layer structure.
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 composition provides improved oxidation and fatigue resistance, reducing thermal expansion mismatch and promoting uniform oxide growth kinetics, thus extending the lifespan of turbine engine components.
Implementation Method 1
reduces the thermal expansion mismatch between the coating and common turbine alloys
Implementation Method 2
a thermally grown oxide of alumina is grown between the bond coat and the TBCs topcoat
Implementation Method 3
promoting uniform oxide growth kinetics
Implementation Method 4
a thermally grown oxide of alumina is grown between the bond coat and the TBCs topcoat
Data Source
AI summary
The present disclosure relates to an improved low-cost metallic coating to be deposited on gas turbine engine components. The metallic coating consists of 1.0 to 18 wt % cobalt, 3.0 to 18 wt % chromium, 5.0 to 15 wt % aluminum, 0.01 to 1.0 wt % yttrium, 0.01 to 0.6 wt % hafnium, 0.0 to 0.3 wt % silicon, 0.0 to 1.0 wt % zirconium, 0.0 to 10 wt % tantalum, 0.0 to 9.0 wt % tungsten, 0.0 to 10 wt % molybdenum, 0.0 to 43.0 wt % platinum, and the balance nickel.