Infrared Window Composite Coating for Impact Resistance
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Solution Overview
Problem
Current materials used in optical guidance systems for armaments, such as sapphire, are susceptible to damage from impact and erosion, and lack the necessary combination of impact resistance, mechanical strength, and transparency to infrared radiation.
Innovation Solution
A composite coating with a compositional gradient is applied over a substrate, comprising a first phase with properties matching the substrate and a second phase with higher erosive wear resistance, where the second phase is present in higher concentration at the external surface, and the coating is designed to transmit infrared radiation with minimal scattering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sapphire is used as window material, then infrared transparency is achieved, but impact and erosion resistance is insufficient
Solution Approach 1:
The patent applies composite materials by combining sapphire substrate with a gradient coating comprising multiple phases (first phase with CTE matching substrate, second phase with higher erosion resistance). This composite structure allows the window to simultaneously achieve infrared transparency from the sapphire base and enhanced erosion/impact resistance from the gradient coating, directly resolving the contradiction between transparency and durability.
Solution Approach 2:
The patent implements local quality through a compositional gradient in the coating, where the first phase (optically compatible with substrate) is concentrated near the substrate interface and the second phase (erosion resistant) is concentrated at the external surface. This spatial variation in material composition allows different regions to optimize for different functions: optical compatibility at the interface and erosion resistance at the surface, thereby resolving the contradiction between maintaining transparency and achieving erosion resistance.
2Reliability
If coating composition is changed to improve erosion resistance, then wear resistance is improved, but thermal stress compatibility with substrate may be compromised
Solution Approach 1:
The patent applies local quality by spatially distributing different phases in the gradient coating. The first phase, with CTE matching the substrate, is positioned near the substrate interface to maintain thermal stress compatibility, while the second phase, with higher erosion resistance, is positioned at the external surface. This local differentiation resolves the contradiction between erosion resistance and thermal stress compatibility.
Solution Approach 2:
The patent implements parameter changes by gradually varying the composition parameters (phase distribution, concentration gradients) through the coating thickness. The CTE parameter is controlled to match the substrate near the interface, while erosion resistance parameters are optimized at the surface. This continuous parameter variation allows simultaneous satisfaction of both thermal stress compatibility and erosion resistance requirements.
3Strength
If coating is made thicker to improve impact resistance, then mechanical strength is improved, but infrared transmission is reduced
Solution Approach 1:
The patent applies local quality by creating a gradient coating where the optical properties are optimized near the substrate interface (first phase dominant) and mechanical/erosion properties are optimized at the external surface (second phase dominant). This allows the coating to maintain thin overall thickness while achieving both good infrared transmission through the optically compatible first phase and adequate impact resistance through the erosion-resistant second phase at the surface.
Solution Approach 2:
The patent uses composite materials with complementary properties: the first phase provides optical compatibility and infrared transmission, while the second phase provides erosion and impact resistance. The gradient distribution of these composite phases allows the coating to achieve both transmission and strength without requiring excessive thickness, resolving the contradiction between impact resistance and infrared transmission.
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 enhanced impact and erosion resistance, mechanical strength, and maintains high infrared transparency, reducing thermal stresses and scattering losses, while ensuring the optical and mechanical compatibility of the coating with the substrate.
Implementation Method 1
The coating and the substrate are capable of transmitting infrared radiation
Implementation Method 2
The coating and substrate together cause scattering of up to about 5% of incident infrared radiation
Implementation Method 3
The first phase has at least one property selected from the group consisting of a) a coefficient of thermal expansion (CTE) that is within about plus or minus 3 parts per million per degree centigrade of a CTE of the substrate
Data Source
AI summary
Articles transparent to infrared radiation and resistant to impact and wear are provided. The article comprises a substrate and a composite coating disposed over the substrate and extending from an interface with the substrate to an external surface. The composite coating comprises a first phase and a second phase. The second phase has a higher resistance to erosive wear than the first phase. The coating comprises a compositional gradient proceeding from a first composition at the interface of the coating with the substrate to a second composition at the external surface, the first composition comprising a higher concentration of the first phase than that of the second composition.