Nickel-Free Titanium Alloy Nitriding for Biomedical Devices
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Solution Overview
Problem
Current titanium-based alloys for biomedical applications face challenges such as nickel allergenicity, poor machinability, and inadequate surface biocompatibility, particularly in devices with complex shapes, due to non-uniform nitride layer deposition techniques and limited mechanical properties.
Innovation Solution
A method for manufacturing a nickel-free titanium-based alloy with superelastic and/or shape memory properties, involving vacuum fusion, homogenization, mechanical shaping, and a gaseous atmosphere heat treatment for nitriding, which forms a uniform nitride, carbonitride, or oxynitride layer to enhance surface hardness and biocompatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If plasma-based nitride deposition is used to improve surface biocompatibility, then surface treatment is achieved, but uniform deposition is not possible especially in difficult-to-access areas
Solution Approach 1:
The patent replaces the plasma-based physical deposition system with a chemical nitriding system using gaseous ammonia or nitrogen. This chemical substitution allows the nitriding atmosphere to penetrate and react uniformly with the titanium alloy surface throughout the entire component, including complex geometries and hard-to-reach areas, achieving uniform nitride layer deposition that plasma methods cannot provide.
Solution Approach 2:
The patent introduces a gaseous nitriding medium (ammonia or nitrogen) as an intermediary that can uniformly distribute and react with the alloy surface. This gaseous intermediary penetrates all surfaces including concavities and complex shapes, ensuring uniform nitride formation throughout the component rather than only on externally accessible surfaces.
2Strength
If nickel is added to titanium alloy to achieve superelasticity and shape memory properties, then mechanical properties are improved, but nickel allergenicity and inflammatory reactions occur
Solution Approach 1:
The patent extracts and removes nickel from the titanium alloy composition entirely. By eliminating the nickel element from the alloy formulation, the invention eliminates the source of allergenicity and inflammatory reactions while maintaining the desired mechanical properties through alternative alloying elements and microstructure control.
Solution Approach 2:
The patent changes the compositional parameters of the alloy by substituting nickel with other elements (such as aluminum, vanadium, or zirconium) and adjusts the microstructural parameters through controlled cooling rates and heat treatments. This parameter modification allows achieving superelasticity and shape memory properties through martensitic transformation in nickel-free titanium alloys.
3Object-affected harmful factors
If nickel-free titanium alloys are used to eliminate allergenicity, then biocompatibility is improved, but machinability deteriorates causing premature breakage
Solution Approach 1:
The patent modifies the microstructural parameters of the nickel-free titanium alloy through controlled cooling rates during solidification and subsequent heat treatments. By optimizing the grain structure, phase distribution, and hardness parameters, the invention achieves a balance where the alloy maintains its biocompatibility while improving machinability and resistance to premature breakage during manufacturing.
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 produces an alloy with improved mechanical properties, enhanced biocompatibility, and increased surface hardness, wear resistance, and machinability, while maintaining the metastable beta microstructure for superelastic effects, suitable for complex biomedical devices.
Implementation Method 1
said heat treatment phase is carried out in a gaseous atmosphere, and also constitutes a so-called nitriding phase, carrying out a surface treatment by reaction with said gas, so as to form homogeneously on the surface, a layer of nitride, carbonitride, oxynitride
Implementation Method 2
optionally, homogenization of the ingot under vacuum by annealing at a first temperature, in particular greater than 900° C., consisted of raising the temperature of the ingot, maintaining it at this temperature for a period allowing complete homogenization of the first quench
Implementation Method 3
preparation by fusion under vacuum of the various constituent metals of the desired alloy, to produce an ingot
Data Source
Figure 1~4
Figure 2~5B
AI summary
The invention relates to a method for manufacturing a titanium alloy having superelastic properties and/or shape memory for biomedical use, which comprises the steps of: preparing an ingot by melting the various metals that form the desired alloy in a vacuum; optionally homogenizing the ingot in a vacuum by high-temperature annealing (higher than 900° C.); first quenching; mechanical shaping (rolling, drawing, machining or the like); heat treatment for redissolution in beta phase beyond the beta transus temperature (until a second temperature and then maintaining same for a certain time); and second quenching; characterized in that said heat treatment phase is carried out in a gaseous atmosphere and also constitutes a surface treatment suitable for forming on the surface a layer of nitride, carbonitride, oxide, oxynitride or the like.