How to Turn Titanium Alloys: Geometry, Speeds, and Coolant

Turning titanium requires careful selection of speed and feed because cutting temperatures are high. The preferred cutting-temperature range is 480-540°C for high-speed-steel tools and 650-750°C for carbide tools. Workpiece deformation, thermal distortion, and tool wear also influence dimensional accuracy.

1. Turning-Tool Geometry

For all three tools, the recommended nose radius is 0.5-1.5 mm, the auxiliary land width is 0.05-0.3 mm, and the auxiliary rake angle is 0-10°. Keep rake and flank surfaces very smooth. A sharpened edge must be free of burrs, burns, notches, and cracks. Grind carbide with a diamond wheel. The chip-breaker groove-bottom radius should be 6-8 mm.

2. Cutting Data for Titanium Alloys

Starting Data for Ti-6Al-4V

With an indexable turning tool, cutting speed may be increased appropriately when cutting fluid is used.

Speed Correction by Alloy Group

Speed Correction by Depth of Cut

Turning Through an Oxide Layer

3. Cutting Fluids for Titanium Turning

4. Cutting-Fluid Precautions

1. Chlorinated fluids can decompose at cutting temperature and release hydrogen, which titanium may absorb and which can cause hydrogen embrittlement.
2. Chlorine can react with titanium to form titanium chloride and cause corrosion. Keep chloride below 0.02% by mass.
3. Because chlorides can promote stress-corrosion cracking, avoid chlorinated cutting fluids.
4. Clean the workpiece promptly after cutting so residual chloride cannot attack the surface.
5. Use a flow rate of at least 15-20 L/min.
6. The fluid needs both strong cooling and extreme-pressure lubrication. Maintain machine-tool guideways carefully when using water-based fluid.

5. Additional Precautions

1. Do not allow lead- or zinc-based tooling and fixtures to contact titanium parts. Copper-tin, cadmium, and their alloys are also prohibited for contacting tools and fixtures.
2. All tools, fixtures, and devices that contact titanium must be clean. Protect cleaned titanium parts from grease and fingerprints because later salt contamination can contribute to stress-corrosion cracking.