Anodic Oxide Coating Thermal Expansion Matching
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Solution Overview
Problem
Anodic oxide coatings are susceptible to thermally induced cracking due to differences in thermal expansion coefficients between the metal substrate and the oxide coating, leading to cosmetic and functional issues when exposed to high temperatures.
Innovation Solution
Incorporating a material with a higher thermal expansion coefficient into the pores of the anodic oxide coating to match the expansion of the metal substrate, thereby reducing the stress and preventing cracking during thermal exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sealed anodic oxide coating is applied to provide good wear and corrosion resistance, then protection is improved, but the coating becomes susceptible to cracking when exposed to high temperatures
Solution Approach 1:
The patent changes the thermal expansion parameter of the anodic oxide coating by incorporating particles with higher thermal expansion coefficients into the coating matrix. This modifies the coating's thermal expansion behavior to better match the substrate, reducing thermal stress during temperature cycling and preventing crack formation while maintaining corrosion resistance
Solution Approach 2:
The patent creates a composite anodic oxide coating by incorporating particles (such as metal oxides or ceramics) with higher thermal expansion coefficients into the porous anodic oxide structure. This composite structure combines the protective properties of the anodic oxide with the thermal expansion characteristics of the high-expansion particles, achieving both corrosion resistance and thermal stability
2Duration of action of stationary object
If the anodic oxide coating thickness is increased to enhance protection, then durability is improved, but thermally induced cracking becomes more severe
Solution Approach 1:
The patent modifies the thermal expansion parameter of thick anodic oxide coatings by incorporating particles with higher thermal expansion coefficients. This parameter change allows the coating to expand and contract more closely with the substrate during temperature variations, reducing the tensile stress that would otherwise cause cracking in thicker coatings and enabling enhanced durability without thermal damage
3Strength
If the thermal expansion coefficient of the coating is kept low to match the substrate, then cracking is reduced, but the coating cannot accommodate thermal expansion differences
Solution Approach 1:
The patent creates a composite structure where particles with high thermal expansion coefficients are dispersed within the anodic oxide coating matrix. This composite approach allows the coating to exhibit intermediate thermal expansion characteristics - not matching the substrate perfectly but providing sufficient compliance to accommodate thermal differences without cracking, thus achieving both crack resistance and thermal expansion accommodation
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 modified anodic oxide coating becomes resistant to thermally induced cracking, allowing for higher temperature exposures without cosmetic damage and maintaining corrosion protection, even at thicknesses of 10 micrometers or more.
Implementation Method 1
The material has a higher thermal expansion coefficient than that of the metal oxide. The incorporated material increases an in-plane thermal expansivity of the sealed anodic oxide coating such that the sealed anodic oxide coating resists cracking when the anodized substrate is exposed to a target temperature.
Implementation Method 2
Anodizing is a method of providing an anodic oxide coating on a metal substrate. During an anodizing process, a portion of the metal substrate is converted to a metal oxide, thereby forming a protective oxide layer or coating.
Implementation Method 3
During an anodizing process, a portion of the metal substrate is converted to a metal oxide
Data Source
AI summary
A process is disclosed for minimizing the difference in thermal expansivity between a porous anodic oxide coating and its corresponding substrate metal, so as to allow heat treatments or high temperature exposure of the anodic oxide without thermally induced crazing. A second phase of higher thermal expansivity than that of the oxide material is incorporated into the pores of the oxide in sufficient quantity to raise the coating's thermal expansion coefficient. The difference in thermal expansion between the anodic oxide coating and underlying metal substrate is reduced to a level such that thermal exposure is insufficient for any cracking to result. The second phase may be an electrodeposited metal, or an electrophoretically deposited polymer. The second phase may be uniformly deposited to a certain depth, or may be deposited at varying amounts among the pores.