What to know about machining Titanium
Titanium alloys have recently become popular materials for various industrial applications. They are widely used in the aerospace and medical industries, particularly to make the latest aircraft designs and body implants.
Titanium alloys boast an immunity to corrosion, a high strength-to-weight ratio, and excellent mechanical properties. The metal mineral surface reacts with oxygen resulting in a 10nm deep chemically stable solid oxide surface layer (TiO2) that gives the mineral excellent chemical and corrosion resistance.
Machining of titanium alloys
Machining of titanium alloys may involve the following processes and their operations:
- Conventional machining
- Face milling
- CNC milling
- High-speeded cutting
- Forming operations
- Hot and cold forming
- Alternative machining operations
- Water-jet cutting
- Direct metal laser sintering
- Laser cutting
Chemical properties of Titanium
While titanium alloys have desirable properties, they are not easy workpiece materials. The reason is that titanium mineral has the following inherent chemical properties.
High chemical reactivity
Welding is a common problem during titanium machining; at high temperatures, the mineral can weld to the cutting tool resulting in chipping or reduced tool life
Low thermal conductivity
Titanium doesn’t absorb heat from the cutting surface quickly enough, and this may affect your tool’s life
Low elastic modulus
Titanium’s elasticity causes it to spring away from cutting tools, causing edges to rub instead of cutting, resulting in friction that increases heat at the cutting surface
Given the physical and chemical qualities of titanium alloys and their poor machinability, evaluating and selecting the appropriate metalworking fluid, tools, and practices are critical. Here are some tips and equipment recommendations for machining titanium.
What cutting fluids to use when machining Titanium
The best fluids for machining titanium are water-based, as opposed to straight oils or chlorinated fluids. Water is just more efficient at removing heat and cooling the materials than straight oils. On the other hand, chlorinated cutting fluids make the titanium vulnerable to stress corrosion.
For reduced-speed and high-intense cutting operations, water-based fluids rich in phosphorus EP and sulfur additives reduce tool wear and offer the best performance.
Machining parameters and practices for Titanium workpieces
Besides cutting fluid selection, studies also show that certain machining practices and parameters boost titanium machinability. Applying water-based lubricants at high volume, slower cutting speeds, and higher cutting depths are recommended. The reason for slower cutting speed and high-volume lubricant applications is to reduce heat and pressure.
It’s also a smart idea to get machining programs that reduce the amount of time the cutting tool spends in the titanium because the more the contact time, the more the heat produced.
The recommended cutting tools are those made of Polycrystalline Diamond (PCD) and Cubic Boron Nitride (CBN). The recommended cutting speed range is 12 -80 m/min and roughly 50 % slower when using high-speed steel cutting tools.
Also, titanium’s lower elastic modulus gives it a tendency to spring back or deflect when cutting and should therefore be placed in a more rigid setup with greater clearances for the cutting tools.
Apart from conventional machining operations, you can also do forging, water-jet cutting, laser cutting operations, and direct metal laser sintering. It’s recommended that any forging operation take place below 925 Celsius. Meanwhile, direct metal laser sintering is a more friendly technique involving layer-by-layer building based on computer tomography models and specific 3D data resulting in greater detail.
Titanium has excellent physical and chemical properties making it a popular choice for various industrial applications. However, it has poor machinability; therefore, certain machining practices and parameters must be followed for more efficient operations. A combination of WC-Co-rich carbides, slower cutting speeds, and high-volume applications of water-based lubricants are just some of the recommended practices.
Looking for machines and tools for machining Titanium? Contact us! We service and source parts for virtually all machines.