Nitinol
- DeSta::Microcut
What exactly is Nitinol?
Nitinol is probably the best-known shape memory alloy. Alloys of this type are also known as memory metals because they appear to be able to ‘remember’ a previous shape even though they have been severely deformed in the meantime.
The word nitinol is an acronym of Nickel Titanium Naval Ordnance Laboratory. The nickel-based alloy has special properties that are attributable to the NiTi intermetallic phase. This has an ordered cubic crystal structure that differs from that of titanium and nickel. The material consists mainly of nickel (approx. 55%) and a significant proportion of titanium. The density of Nitinol is around 6.4 g/cm³. The alloy is high-strength and corrosion-resistant, but is pseudoelastically deformable up to around 8%. The alloy can be used at temperatures of up to 500 °C.
What are the specific properties of Nitinol?
The transformation temperature is influenced by the alloy ratio. If the transformation temperature is 80 °C, for example, a component made of this alloy can be bent with little force at room temperature. As soon as the component is heated above the transformation temperature, it returns to its original shape. Colloquially, such alloys are referred to as ‘memory metal’ or ‘shape memory metal’.
If the alloy has a low transformation temperature of 0 °C, it is colloquially referred to as ‘superelastic’. The material behavior at room temperature is similar to that of spring steel and has a high formability. Regardless of the alloy, Nitinol is a corrosion-resistant material.
How is Nitinol processed?
The basic shape of a component can be embossed by annealing at around 500 °C. Due to the raw materials used, Nitinol is not an inexpensive material. Even minor impurities have a negative impact on the desired material properties. As a result, Nitinol is rarely used in mass production.
The material has a high hardness. DeSta::Microcut only cuts the material using waterjet cutting systems, as high temperatures have a negative impact on the material structure. The thermal separation process of laser fine cutting is therefore not used for Nitinol.
What surface treatments are possible for Nitinol?
Nitinol is used for high-quality, functional applications with a long service life. A final chemical or electrochemical surface treatment suitable for the material is very important. The following surface treatments are possible for Nitinol:
SandblastingThe method is highly effective in removing burrs, surface contamination and other surface defects. The mechanical surface treatment has a positive effect on the fatigue life of the components.
PicklingOxide layers and residues on the surface are removed by the process. The process produces silvery bright and silky glossy surfaces. During the pickling process, attention must be paid to the hydrogen embrittlement that occurs, which has an unfavorable effect on the material behavior.
ElectropolishingThe process delivers the highest quality in terms of biocompatibility, passivity, corrosion resistance, purity and cleanability. It also produces high-gloss surfaces. Electropolishing is used in particular in the manufacture of Nitinol stents.
Why DeSta GmbH & Co KG ?
DeSta::Microcut stands for innovative ideas, creativity in problem solving, consistent quality and many years of experience in laser fineblanking. DeSta::Microcut’s modern machinery and highly qualified employees ensure that customers’ individual components are manufactured with the utmost care and precision.
From complex shapes to fine details, almost any requirement can be realized. The company also manufactures from a batch size of one to small and medium series.
In which industries is Nitinol used?
The material is frequently used in medicine, for example as Nitinol wire, but also in the form of spatulas. Due to its special properties, Nitinol is also used in other sectors such as the aerospace, electronics, energy and mechanical engineering industries. Due to its shape memory in particular, the material is often used for mechanical components that are activated or moved by temperature changes.
What are the advantages of Nitinol in medical technology?
Nitinol is an established material in medical technology due to its strong shape memory effect and superelasticity. Biocompatible Nitinol also impresses with its high corrosion resistance and good compatibility when used in implants, as no Nitinol allergies are known.
Nitinol is used in surgical tools, endoscopes and implants such as artificial heart valves and stents. Endovascular stents are often used in vascular surgery as a kind of support to protect arteries and veins. Particularly when used to support the coronary arteries, the Nitinol stent enables millions of patients to live longer with a significantly better quality of life. Another special feature of Nitinol is that the material is non-ferromagnetic and can therefore be used for imaging procedures such as MRI.
Nitinol wire is used in the dental industry for dental braces. The unique material makes it possible to file around corners with special root canal files made from Nitinol. In surgery, super-elastic nails made from the material are used to connect bones after complicated fractures.
Which temperature ranges are relevant for the shape memory effect of Nitinol?
The use of shape memory alloys, also known as memory metal, is suitable for various temperature ranges. Geometric shapes made of Nitinol can be bent at room temperature with little force. To permanently shape Nitinol, the workpiece is heated to over 500 °C in the desired position. The so-called transformation temperature indicates the temperature at which the workpiece returns to its original shape. This is between -20 and +110 °C, depending on the composition of the alloy. The melting temperature of the alloy, which consists largely of nickel, is between 1,240 and 1,328 °C.
Which quality control measures are relevant when processing Nitinol?
DeSta::Microcut relies on CNCwaterjet cutting when processing the nickel alloy. This ensures high cutting accuracy with minimal material loss of Nitinol sheets, for example. The application of high temperatures to the cutting edge, as is the case with Laser fineblanking changes the material properties of Nitinol and is therefore avoided.
The aim of DeSta::Microcut is to fully satisfy your requirements and to meet high quality standards. This is guaranteed, among other things, by continuous measurements during production and DIN EN ISO 9001 certification. Optical 2D and 3D measuring methods are available in our in-house measuring room. If required, detailed measurement reports and initial sample test reports (EMPB) can also be produced.
