Nitrided Titanium Surface Hardness and Color Restoration
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Solution Overview
Problem
Titanium and its alloys used in consumer electronics enclosures lack sufficient hardness and strength for wear resistance, and the nitriding process results in an unattractive gold/brown color that consumers find aesthetically unappealing.
Innovation Solution
A controlled nitriding process is applied to titanium substrates, followed by anodization and chemical etching to strip away the titanium nitride layer, maintaining the increased hardness while restoring the natural titanium color by removing less than 1 μm of material from the external surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a nitriding process is applied to titanium to increase hardness and wear resistance, then the hardness and strength are improved, but the surface color changes to an unattractive gold/brown hue
Solution Approach 1:
The patent segments the nitrided surface into two functional zones: a thin upper layer (less than 1 micrometer) that is removed to restore aesthetic appearance, and a deeper hardened zone that retains wear resistance. This segmentation allows simultaneous achievement of both hardness and attractive color.
Solution Approach 2:
The patent extracts only the necessary minimum amount of material (less than 1 micrometer) from the nitrided surface to remove the gold/brown color while preserving the underlying hardened structure. This extraction restores the natural titanium color while maintaining the hardness benefits of nitriding.
2Ease of manufacture
If material is removed from the nitrided surface to restore natural titanium color, then the aesthetic appearance is improved, but the hardness and wear resistance may be reduced
Solution Approach 1:
The patent applies local quality by creating a highly hardened zone at specific depths below the surface while keeping the very thin surface layer (less than 1 micrometer) removable. The hardness profile is optimized locally at different depths, with maximum hardness at the surface-adjacent zone and sufficient hardness extending deeper to provide wear resistance.
Solution Approach 2:
The patent uses partial action by removing only a small portion (less than 1 micrometer) of the nitrided layer, which is sufficient to eliminate the unwanted color but insufficient to compromise the underlying hardened structure. This partial removal achieves the aesthetic goal while preserving mechanical properties.
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 method achieves elevated hardness exceeding 850 Hv while returning the color to a natural titanium hue, characterized by L* > 70, a* < 1, and b* < 5, thus addressing both strength and aesthetic concerns.
Implementation Method 1
titanium and its alloys thereof may be insufficient to provide sufficient hardness and strength to protect operational components carried by these enclosures. Although titanium and its alloy thereof are capable of undergoing a 'case-hardening' process
Implementation Method 2
a titanium substrate having interstitial nitrogen atoms
Implementation Method 3
forming an anodized nitrided part from the nitrided titanium substrate, wherein the anodized nitrided part includes an anodized layer overlaying the nitrided titanium substrate
Implementation Method 4
forming a nitrided part by removing the anodized layer of the anodized nitrided part
Data Source
AI summary
This application relates to an enclosure for a portable electronic device. The enclosure includes a titanium substrate having interstitial nitrogen atoms, where the titanium substrate is characterized as having an a* value that is less than 1, a b* value that is less than 5, and an L* value that is more than 70.