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Titanium is twice as strong as aluminum, has the highest strength-to-weight ratio of any metal, and is bio-compatible. These qualities make it a preferred material for products that need to endure harsh conditions. But does this strength present challenges for machining titanium?
Find out through this article that unveils the journey of CNC Machining Titanium. It mentions the machining challenges, the common titanium grades, and applications of machined titanium.
Why Choose Titanium for CNC Machining?
Titanium’s history is relatively recent. It was first isolated in the 20th century by Hunter and saw its initial commercial use in military applications by the Soviets in the mid-century. Over time, it became popular in the aviation and marine industries.
But, what makes it suitable for CNC machining? The following characteristics:
Corrosion Resistance
Titanium is corrosion-resistant – it forms a thin, stable oxide layer on its surface, the second it’s exposed to air. The titanium oxide layer acts as a barrier and further prevents oxidation or corrosion.
Lightweight
Titanium has strength comparable to that of steel but weighs 40% less. Its density is about 4.5 g/cm³, compared to steel’s density of around 7.8 g/cm³. That’s beneficial in aerospace industries and where weight is critical.
Bio-Compatible
Titanium is bio-compatible due to its inert nature and excellent corrosion resistance in biological environments. It does not react with bodily fluids or cause an immune response. So, it’s an ideal material for medical implants and prosthetics.
High Strength-to-Weight Ratio
Titanium’s strength-to-weight ratio is one of the highest among metals. It is twice as strong as aluminum while being only 1.67 times heavier, which gives it a superior strength-to-weight ratio.
Non-Magnetic
Titanium is paramagnetic i.e. with weak magnetic properties. Its non-magnetic nature helps reduce interference in machining processes where magnetic materials could disrupt equipment.
Challenges in CNC Machining Titanium
Titanium has many desired characteristics, but some of these properties, strength, for instance, pose a challenge for machining.
Galling and Gumming
Pure titanium has a low modulus of elasticity but a high strength. These contrasting properties turn it into a gummy material during machining. This leads to poor chip formation and increases the likelihood of galling.
Heat Build-Up
Titanium is a poor conductor of heat, which causes heat to accumulate at the cutting edge and workpiece interface, particularly at high machining speeds. This heat buildup accelerates wear and tear on both the tool and the workpiece.
Elastic Deformation
The low modulus of elasticity also results in material deformation. Its unsupported sections can deform during machining, making it challenging to maintain dimensional accuracy, especially when thin parts are involved.
Moreover, it tends to spring back after deformation, which can further cause challenges in achieving the right tolerances.
High Cutting Forces
Due to their crystal structure and inherent hardness, titanium alloys require high cutting forces, which increases the difficulty in machining, tool wear, and energy consumption during cutting processes.
Work Hardening
Titanium tends to work harden during machining i.e. the material surface becomes harder and harder after every cut. That makes subsequent cuts more difficult, causing additional tool wear.
Best Titanium Grades for Machining
There are around 50 known titanium grades, though ASTM recognizes 31 of them. Based on their properties and composition, titanium alloys are categorized into three main types: alpha alloys, beta alloys, and alpha-beta alloys.
Alpha-Titanium Alloys
Alpha-titanium are commercially pure titanium alloys with small amounts of aluminum or iron for stabilization. They have excellent high-temperature stability, corrosion resistance, and durability. Although they may not be as ductile as other titanium types, they are lightweight and formable. Titanium Grades 1 to 4 fall in this group.
- Titanium Grade 1 is commonly used due to its excellent machinability and formability. It is the softest and most ductile of all titanium grades. However, its lower strength compared to other grades limits its use in more demanding structural applications.
- Titanium Grade 2, also called the “workhorse” of titanium, offers a balance of high corrosion resistance, strength, formability, and weldability. It is cost-effective, which makes it a favorable choice for welding and anodizing.
| Grade | Composition | Ultimate Tensile Strength (MPa) | Rockwell Hardness | Applications |
| Titanium Grade 1 | 99% Ti 0.2% Fe 0.18% O N, C, H (Trace Amounts) | 240 | B32 | Plating, Piping |
| Titanium Grade 2 | 99% Ti 0.3% Fe 0.25% O N, C, H (Trace Amounts | 345 | B55 | Anodizing, Welding, Lining Material |
Beta-Titanium Alloy
Beta titanium alloys are stabilized with elements such as vanadium, palladium or molybdenum. In terms of strength, they are similar to alpha alloys but more ductile and formidable, which makes them better for complex forming.
Titanium Grade 11 is a popular alloy in this category. It offers excellent corrosion resistance, particularly in acidic environments, similar to Grades 1 and 2.
| Grade | Composition | Ultimate Tensile Strength (MPa) | Rockwell Hardness | Applications |
| Titanium Grade 11 | 99.75% Ti 0.25% Pd | 240 | B32 | Chemical Processing, Welding, Pumps, H.Es |
Alpha-Beta Titanium Alloy
These alloys share a mix of properties of both alpha and beta types. You’ll see a balanced mix of strength, ductility, corrosion resistance, and high-temperature stability.
Titanium Grade 5 is the most widely used titanium alloy, accounting for about half of all the titanium used globally. It can be heat-treated to improve its mechanical properties further.
Titanium Grade 9 is another balanced titanium alloy. It is easier to machine than Grade 5, making it a preferred choice for certain CNC machining applications.
| Grade | Composition | Ultimate Tensile Strength (MPa) | Rockwell Hardness | Applications |
| Titanium Grade 5 | 88-90% Ti 5.5-6.75% Al 3.5-4.5% V | 950 | C30 | Aerospace components, medical implants, 3D printing |
| Titanium Grade 9 | 94.5% Ti 3% Al 2.5% V | 900 | B90 | Marine and aerospace parts |
Consideration when CNC Machining Titanium
Considering the challenges in mind, these few considerations and tips can help you get the desired result out of machining magnesium:
Selection of the Right Grade
Titanium is expensive, and a wrong grade selection can quickly escalate the project’s price. So, you’ve to choose wisely. For example, if your project involves significant material removal, Grade 2 titanium is a better choice due to its higher machinability. On the other hand, if your application requires high strength at extreme temperatures, Grade 5 titanium is more suitable.
Design Recommendations
Titanium is well suited for multiple product applications but still, you need to validate if machining that particular dimensions is feasible. For example, the minimum wall thickness achievable for titanium parts usually ranges between 0.5 mm to 0.8 mm.
When it comes to machining features like undercuts, square profiles, full radius profiles, and dovetail profiles can be created, but careful consideration must be given to depth. For instance, the hole depth should not exceed 12 times the diameter of the drill bit, and for end mills, the depth should not go beyond 10 times the tool diameter.
Cutting Tools
Machining titanium requires dedicated tools due to its toughness and springy nature. Standard tools aren’t effective. Carbide-tipped tools with a physical vapor deposition (PVD) coating are highly recommended. Nowadays, tools with titanium aluminum nitride (TiAlN) coating are available – they are even more effective.
Sharp tools are crucial when cutting titanium, as its elastic properties can cause a dull tool to rub rather than cut, causing chatter.
In the case of CNC milling, keep in view the number of flutes on end mills. Use tools with more flutes to reduce vibration and improve the overall machining process. For instance, 10 flute end mills are effective in milling titanium. High-feed mills are another option, particularly when dealing with axial and radial cuts.
Cutting Speed and Feed Rate
Titanium tends to get hard as it is cut, which makes more abrasive to the tool. So, a constant feed rate is recommended. If your machine allows, increasing the feed rate can help reduce heat buildup by minimizing the time the tool spends in one area.
For finishing operations, use very light cuts with minimal tool contact, but be aware that this can make it harder to dissipate heat. Therefore, you need to have a high-pressure coolant system in place all the time.
In some cases, an alternative cutting strategy could be increasing the axial depth of cut while reducing radial engagement. This can help improve cutting efficiency and reduce machining temperature.
Material Fastening
The elastic nature requires of material careful clamping. Use CNC machines with a rigid setup and high-quality tooling arrangements. You may also use shorter cutting tools to minimize tool deflection and improve stability during the cutting process.
Finishing Techniques for Titanium Post-Machining
After machining, titanium may undergo any of these finishing purposes to achieve the desired look and feel:
- Anodizing: An electrochemical process to enhance the corrosion resistance and allow colorization of the material. It does so by increasing the thickness of the oxide layer on titanium
- Passivation: It is a chemical treatment that removes surface contaminants, keeping the oxide layer corrosion-free.
- Powder Coating: A powder (usually polymer) is applied and baked onto the titanium surface to create a durable, corrosion-resistant coating.
- Case Hardening: It’s a heat treatment process to harden the surface of a metal while keeping the inner core softer and more ductile. This is done by introducing carbon or nitrogen to the surface through carburizing or nitriding.
- Bead Blasting: A surface finishing technique that uses fine abrasive particles to clean and smooth the titanium surface, creating a uniform matte finish.
Applications of CNC Machining Titanium Parts
Titanium’s unique combination of properties makes it a preferred material in various industries:
Medical Industry
Titanium’s biocompatibility makes it ideal for implants like joint replacements and dental implants, where it must coexist with human tissue without causing rejection.
Aerospace
Its high strength-to-weight ratio is invaluable in aerospace, where the aircraft engines and fasteners must withstand extreme stresses while contributing to overall weight reduction for fuel efficiency.
Military Applications
The corrosion resistance and strength make it a key material for military applications, especially armored vehicles, and naval vessel components. Its ability to endure harsh conditions further guarantees reliability in critical operations.
Marine Industry
The marine sector benefits from titanium’s resistance to saltwater corrosion. It’s ideal for making propeller shafts, hull fittings, and underwater connectors that face constant exposure to harsh environments.
Chemical Processing
Since most titanium alloys are corrosion-resistant, they easily face off aggressive chemical environments. That makes it suitable for chemical processing equipment like storage tanks and heat exchangers, where stability and strength are crucial.
Power and Energy
In power generation, titanium is used in turbine blades and other components that require high temperature and corrosion resistance.
Choose Rich Conn for Titanium Machining Services
Titanium is a tough material, and it requires a top-tier machining provider. If your project involves machining titanium in any form, Rich Conn is your go-to solution. Why choose us?
We have state-of-the-art machinery and tools for precision cutting within the required time frame. Whether you need turning, milling, or multi-axis machining, our advanced equipment and experienced team are ready to meet your project’s needs.Contact us today and book our CNC metal machining services to get started.
