Layered Ceramic Coating for Zirconium Alloy Implants
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Solution Overview
Problem
Current medical implants, particularly zirconium alloy-based ones, face challenges in achieving sufficient abrasion resistance and depth of hardening without compromising surface integrity, especially in hard-on-hard applications where wear rates are high and surface defects can lead to implant failure.
Innovation Solution
A layered ceramic structure is created on a zirconium or zirconium alloy substrate, comprising multiple ceramic layers such as zirconium nitride and zirconium oxide, with a diffusion hardened zone, to enhance surface hardness and depth of hardening, using a process involving ceramic-forming species and reactive gases at controlled temperatures and pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If air oxidation is used to produce thick oxide layers on zirconium alloy, then oxide layer thickness is increased, but dimensional changes occur and abrasion resistance is not significantly improved
Solution Approach 1:
The patent changes the oxidation parameters by controlling temperature (500-900°C), time (1-24 hours), and atmosphere composition to produce oxide layers of specific thicknesses (1-25 microns) without excessive dimensional changes. This resolves the contradiction by finding optimal parameter ranges that balance thickness gain with dimensional stability.
Solution Approach 2:
The patent creates a composite structure with multiple oxide layers (inner layer and outer layer) with different properties. The inner layer provides adhesion and the outer layer provides wear resistance, achieving both thickness and dimensional stability through layered composite architecture.
2Length of stationary object
If air oxidation is continued to produce beige oxide layer, then oxide layer thickness is increased, but micro-cracks form on the surface reducing integrity
Solution Approach 1:
The patent controls oxidation temperature (500-900°C) and time to produce oxide layers that are thick enough (1-25 microns) for wear resistance but below the threshold where micro-cracks form. This parameter optimization resolves the contradiction between thickness and surface integrity.
Solution Approach 2:
The patent maintains continuous oxidation under controlled atmosphere to produce a uniform, crack-free oxide layer. By keeping the oxidation process continuous and controlled rather than intermittent or uncontrolled, the oxide layer forms uniformly without the micro-cracks that would compromise integrity.
3Strength
If blue-black oxide layer is produced, then abrasion resistance is improved, but layer thickness is limited
Solution Approach 1:
The patent creates a composite oxide structure with an inner layer (thicker, less dense) and an outer layer (thinner, denser blue-black layer). This composite architecture allows the overall oxide layer to be thicker than conventional blue-black layers while maintaining the abrasion resistance of the outer blue-black layer.
Solution Approach 2:
The patent adds dimensional complexity by creating a two-layer oxide structure rather than a single uniform layer. This multi-dimensional approach allows simultaneous achievement of greater total thickness and maintained surface hardness for abrasion resistance.
4Strength
If oxide layer thickness is increased for hard-on-hard applications, then wear resistance is improved, but surface uniformity and bonding integrity are reduced
Solution Approach 1:
The patent uses a composite two-layer oxide structure where the inner layer provides thickness and the outer layer provides uniformity. This composite architecture resolves the contradiction by allowing thick oxide layers (1-25 microns) for wear resistance while maintaining surface uniformity through the protective outer layer.
Solution Approach 2:
The patent optimizes oxidation parameters (temperature 500-900°C, time 1-24 hours, atmosphere composition) to control oxide layer formation and maintain uniformity even at increased thicknesses. This parameter control allows achieving wear resistance through increased thickness without sacrificing surface uniformity.
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 layered ceramic structure significantly improves the abrasion resistance and toughness of the implant surfaces, reducing wear rates and enhancing the longevity of medical implants by providing a robust and durable interface in both articulating and non-articulating applications.
Implementation Method 1
a diffusion hardened zone in contact with the substrate, the diffusion hardened zone comprising the zirconium or zirconium alloy and a diffusion hardening species
Implementation Method 2
a ceramic zone having a layered structure comprising at least two layers wherein the ceramic zone is in contact with the diffusion hardened zone
Implementation Method 3
a first layer of the ceramic zone comprises zirconium and nitrogen
Data Source
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AI summary
A new composition and medical implant made there from comprises a thick diffusion hardened zone, and layered ceramic surface. Orthopedic implants comprising the new composition, methods of making the new composition, and methods of making orthopedic implants comprising the new composition are disclosed.