Titanium alloy materials have many advantages and disadvantages. Its disadvantages include high hardness, low plasticity, low thermal conductivity, large elastic deformation, and low elastic modulus. Titanium alloys are mainly used to manufacture compressor components of aircraft engines, followed by structural components of rockets, missiles, and high-speed aircraft. Additionally, they are used in the medical field for human bone implants, among other applications. Due to their high precision requirements and difficulty in processing, there are high demands on machining tools.

During the machining process of titanium alloys, the low thermal conductivity will inevitably result in excessively high cutting temperatures. The low specific heat will cause rapid local temperature rise, thereby reducing the tool's lifespan. The low elastic modulus will exacerbate material surface springback, leading to tool wear or edge chipping. In high-temperature environments, strong chemical activity will exacerbate the chemical reactions between titanium alloys and nitrogen, hydrogen, and oxygen, increasing the difficulty of mechanical processing. Additionally, factors such as cutting conditions, tool materials, and cutting processing time will affect the comprehensive efficiency of cutting processing. Therefore, strict control of relevant aspects is necessary during the machining process of titanium alloy materials.

There are various mechanical machining processes for titanium alloy materials, such as electrical discharge machining, milling, turning, grinding, drilling, and tapping. Tool materials, cutting fluids, processing parameters, and tool geometry parameters are all important influencing factors during the mechanical machining process of titanium alloy materials and must be given high attention.

1. Cutting Fluid:

During the cutting process of titanium alloy materials, the use of cutting fluids can reduce the heat of the blade and flush away the chips, thereby reducing cutting forces. Therefore, the use of cutting fluids must be reasonable to improve the surface quality of parts and production efficiency. Currently, commonly used cutting fluids include non-aqueous oil-based solutions, water-based soluble oil-based solutions, and water or alkaline water-based solutions.

2. Tool Materials:

Titanium alloy materials have the disadvantages of high hardness, low plasticity, and low thermal conductivity, which inevitably lead to high cutting temperatures and cutting forces during the processing process, thereby increasing tool wear and reducing tool life. Therefore, selected tool materials must have high wear resistance and strong hardness. Currently, commonly used tool materials include high-speed steel grades, hard alloy grades, coated tools (with strong anti-bonding performance, strong oxidation resistance, and good wear resistance), cubic boron nitride tools (with high thermal hardness and high hardness), and polycrystalline diamond tools (with high hardness, high wear resistance, high thermal conductivity, and low friction coefficient).

3. Tool Geometry Parameters:

In the rough machining process of titanium alloy materials, tools with small front/back angles and high rigidity should be selected. For example, in the rough machining of titanium alloy TC4, the front angle is set between 0° and 3°. In the precision machining process of titanium alloy materials, tools with sharp edges, dense teeth, large front/back angles, and spiral angles should be selected. For example, in the precision machining of titanium alloy TC4, the front angle is set between 8° and 15°. If boring bars or circular turning tools are used to process titanium alloys, the front/back angles are set between 10° and 15°, and 8° and 14° respectively, and the radius of the tool tip arc is set between 0.2mm and 0.6mm. If thread turning tools are used, the front/back angles are set at 0° and 10° respectively. If forming turning tools are used, the front/back angles are set at 5° and 10° respectively. The design of drills must meet the requirements of smooth chip removal. Specifically, the spiral angle is set between 25° and 30°, the spiral groove of the drill bit is polished, and the thickness of the drill core is set at 1/4 of the drill bit diameter. Depending on the situation, the transverse blade is reground to ensure better strength and centering effect of the drill bit. Additionally, the drill point angle is set between 135° and 140°, and the drill back angle is set between 12° and 15° to increase the width and thickness of the cutting. The design of milling cutters must meet the cutting requirements of titanium alloys. For example, for vertical milling cutters, the front/back angles are set between 6° and 8°, and 6° and 12° respectively, the spiral angle is set between 35° and 40° (with 3° in the front section), and the radius of the tool tip arc is set between 0.5mm and 0.6mm. The cutting environment of tapping is often semi-closed, making it difficult for cutting fluid to flow smoothly to the cutting area, and the lubrication and heat dissipation effects are poor. In addition, titanium alloys have a small elastic modulus, making it easy to cause tap breakage or tooth breakage. Therefore, optimizing the geometric parameters of tapping is particularly important, including setting the back angle of the cutting cone section between 6° and 12°, the front angle between 7° and 10°, the cutting cone angle between 5° and 7°30′, and correcting the tooth profile face with a back angle of 1°. The design of reamers must conform to the characteristic of the small elastic modulus of titanium alloys. Specifically, the front/back angles of the reamer are set between 3° and 5°, and 10° respectively, and the cutting edge width is set at 0.15mm.

4. Cutting Processing Parameters of Titanium Alloy Materials:

For intermittent cutting and continuous cutting, suitable turning process parameters should be set.

When cutting titanium alloys, efforts should be made to reduce cutting temperatures and decrease adhesion. Tools with good red hardness, high bending strength, good thermal conductivity, and poor affinity with titanium alloys should be selected. Due to the poor heat resistance of high-speed steel, tools made of hard alloys should be used as much as possible.

Rheniumet Precision has developed super-hard alloy tools for such products by adding precious metals and refining the grains of hard alloy tool materials. Compared with ordinary hard alloy tools, these tools enhance the red hardness and wear resistance, effectively improving tool life and processing efficiency.