Because we at Neeka Tubes are specialists in precision cut-to-length metal tube, people often pick our brains to learn more about the advantages or disadvantages of different tubing materials — and recently, someone asked us about titanium tube. It’s an interesting topic, because titanium is a material that offers some unique benefits but also poses some distinct challenges.
Titanium tube is often used because of its superior chemical resistance, which is well above that of either stainless steel grade 304 or even grade 316. As a high-strength, low-weight material with high corrosion resistance, titanium provides a high strength-to-weight ratio that makes it a good choice for a diverse range of applications. For example, Neeka Tubes makes a variety of parts from titanium, including small diameter radiused tubes for use in the automotive industry and parts for medical applications such as seed casings for brachytherapy. Titanium tube is also very useful in analytical instruments, such as for chromatography and other applications where tubes are required to resist repeated exposure and not interact with many different types of chemicals and otherlative substances.
Another great thing about using titanium in medical devices is that it is biocompatible. That means not only can the human body tolerate the use of titanium (which is important enough), but also it is nonmagnetic — an increasingly important trait as the use of magnetic resonance imaging (MRI) becomes more common in medical diagnostics. Whether we’re talking about a temporarily placed cardiac needle or a (hopefully) permanent bone joint replacement, MRI compatibility is important for any medical device that is inserted or implanted in the body for any length of time and where a slightly magnetic material would be dangerous. Otherwise, what is supposed to be a non-invasive diagnostic test could cause a metal device to be ripped from the body. Needless to that, that is NOT a good outcome!
Another great thing is, just as there are different types of stainless steel, there are many different grades of titanium tube. For instance, ASTM has a variety of standards (principally B265, B348, and B381) relating to the “recipes” for titanium grades used in different applications. If you look at the specs, you will see there are even multiple grades for unalloyed titanium.
In addition, for applications requiring shape memory, you might also consider titanium tube available in the form of NiTi (or nickel titanium, also called nitinol), which is its own, separate category of product. In theory a 50/50 blend of nickel and titanium, NiTi is never exactly that; in fact, it is always a custom blend, having no ASTM specification and with each manufacturer having its own unique, proprietary formula. NiTi is often used to produce medical tubing that requires a high degree of flexibility and kink resistance, such as catheter guidewires, stents, and super-elastic needles for microsurgery. When properly treated, the material offers excellent corrosion resistance
Having such a remarkable variety of options to explore also means it is vitally important to always indicate which particular type and grade you want — whether it is pure titanium, one of the many alloys, or a NiTi formula — whenever you are specifying titanium tube for your product needs.
Of course, no material is all things to all applications, and titanium is no exception. One of the difficulties is that the material is somewhat more brittle and more difficult to draw than stainless steel, making titanium harder to work with. Although titanium can be drawn into a tube, the process does not produce the nice smooth surface that can result when drawing stainless steel. There are companies that can draw titanium down to Ra 8-10 microinch; however, stainless steel can be drawn to a substantially smoother Ra 3-4 microinch or better.
The rougher ID on titanium tube can have an impact on the microfluidic properties of any liquid that needs to move through the tube, which can become an issue in applications where the smooth flow of the liquid is very important. For most medical device applications, where the tube will carry blood and other bodily fluids, this is not an issue; however, turbulence is a serious problem in applications where the tubing will carry tiny fluid volumes.
Being a more brittle and less forgiving material, titanium is also harder to machine. The more you have to do to titanium to achieve your final product, the greater the chances you can have a problem with chipping and other surface roughness issues. Additionally, the machining of titanium requires more coolant than other materials may need; high-pressure coolant must be delivered at precisely the place of machining from multiple nozzles and angles, to flood the area with coolant.
While titanium tube can be machined despite the challenges, titanium is rarely used for the junctures of tubes. Although it is possible to make tube fittings from titanium, it is an extremely difficult and specialized task. In fact, for medical devices in particular, where a lot of machining is required to create flares, swages, and threading at the points of connection, metal *of any kind* is a very small part of the tube fitting market.
Instead, tube fittings for medical devices more often use a similarly inert and MRI compatible material that can be molded or machined more easily. For instance, high durability PEEK (PolyEtherEtherKetone) or other specialized plastics, which are more easily machined and much more forgiving, are more likely to be used for medical device fittings.
Across both the pros and the cons, the issue of titanium’s cost must also be taken into consideration. Historically, because titanium is not used as frequently as a material such as stainless steel, there are only a few smaller vendors that make titanium tube. Additionally, it comes in fewer standard sizes, requiring greater lead time to produce custom sizing, which in turn also adds to the cost. Therefore, titanium tube is a material that you’d better REALLY need — not something to be chosen lightly — if you are going to specify it.
And here’s an added tip: From a practicality standpoint when titanium is absolutely desired for a final product, companies often prototype the product design in another, less expensive metal to test the feasibility and function. If the initial testing validates the design, it can then be retested using titanium.
If titanium IS the appropriate tubing material for your specific application, you can be sure Neeka Tubes can grind, lap, polish, or cut whatever type and grade of titanium tube you might need. We routinely cut, grind, lap, and polish tubes in lengths as short as 0.006″ with wall thicknesses as thin as 0.001″ or IDs as small as 0.001″ in any metal, including titanium. We say that if the diameter can be drawn, we can work with it. We can also cut coated tubing precisely without damaging the coating and while maintaining concentricity and a clean ID. We can also customize tubes with features such as angle cuts, slots, points, and holes.