The whole process of CNC machining of titanium alloy: from material selection to surface treatment

Titanium alloy has become a core material in aerospace, medical devices, 3C electronics and other fields due to its high strength, light weight and corrosion resistance. However, it is difficult to process and cost-sensitive, which puts forward strict requirements on the whole process control. This article systematically analyses the key steps of CNC machining of titanium alloys, covering material selection, process optimization, quality control and surface treatment, to help you master efficient and low-consumption machining strategies.

I. Titanium Alloy Material Selection: Performance and Scene Adaptation

1. Mainstream Titanium Alloy Classification

Industrial pure titanium (Grade 1-4): excellent corrosion resistance, but lower strength (tensile strength of 300-550MPa), suitable for chemical equipment linings, desalination pipelines and other non-load-bearing parts.

TC4 (Ti-6Al-4V): the most widely used in the aerospace field, tensile strength ≥ 895MPa, temperature resistance up to 400 ℃, suitable for engine blades, aircraft skeleton.

Ti-6242 (Ti-6Al-2Sn-4Zr-2Mo): outstanding high-temperature performance (strength retention rate of >80% at 600 ℃), used in rocket nozzles, turbine discs and other extreme environments.

Medical titanium alloys (e.g. Ti-13Nb-13Zr): high biocompatibility, modulus of elasticity close to that of human bone (55 GPa), used for orthopaedic implants and dental instruments.

2. Material Selection Decision Model

Corrosion Resistance Requirement: Preferred Ti-15V-3Cr-3Sn-3Al alloy containing molybdenum (Mo) for marine environment, with twice the corrosion resistance to chlorine ions as TC4.

Balance of lightweight and strength: TC4 ELI (low-gap element version) is preferred for 3C electronic products, with a yield strength of 900MPa and a density of only 4.43g/cm³, 40% lighter than aluminium alloys.

Cost control: Consider titanium alloy powder injection moulding (MIM) for small batch production, increasing material utilisation to 95% and reducing costs by 30%.

II. Titanium alloy CNC machining core challenges and solutions

1. machining difficulties

high cutting temperature: titanium alloy thermal conductivity is only 1/6 of steel, the temperature of the cutting zone can reach 1,000 ℃, accelerating tool wear.

Machining hardening: the deformation zone is easy to form a hardened layer (hardness increased by 20%-30%), resulting in tool chipping and surface defects.

Sticky tool phenomenon: titanium chips are easy to adhere to the tool, causing chip tumour, affecting the surface roughness (Ra>1.6μm).

2. Process optimisation strategy

Tool selection:

Coated carbide tool: Diamond coated (CVD) tool life is extended by 3 times, and the line speed can reach 80-120m/min.

Large front angle design: Front angle of 15°-20° reduces the cutting force by 20%, and inhibits machining hardening.

Optimisation of cutting parameters:

Roughing: cutting speed 50-80m/min, feed 0.1-0.2mm/tooth, back draft 2-4mm.

Finishing: cutting speed 100-150m/min, feed 0.05-0.1mm/tooth, Ra up to 0.4μm.

Cooling and lubrication: high-pressure internal cooling system (pressure ≥7MPa) combined with extreme-pressure cutting fluid to reduce the Cooling and lubrication: high-pressure internal cooling system (pressure ≥ 7MPa) with extreme pressure cutting fluid, reducing cutting temperature by 40%.

III. Typical machining process and process control

1. Thin-walled parts processing cases (aviation hatch cover as an example)

Clamping design: the use of profiled aluminium alloy tooling, with a vacuum suction cup, to reduce the deformation of the clamping (flatness ≤ 0.1mm).

Layered cutting: leave a margin of 0.3mm for rough machining, natural aging for 24 hours to release stress, and then finish machining to a tolerance of ±0.01mm.

Vibration suppression: spindle speed is reduced by 10%, and adopting the strategy of smooth milling + variable depth of cut, the amplitude of vibration is reduced by 50%.

2. Thread and deep hole processing

Thread processing: titanium alloy tapping is easy to break the taper, it is recommended to use thread milling, the speed of 2000rpm, pitch error <0.02mm.

Deep hole drilling: gun drilling process with the BTA internal cooling system, the depth to diameter ratio of up to 30:1, the straightness error ≤0.05mm/m.

IV. Surface treatment and post-process

1. Deburring and polishing

Mechanical polishing: rough polishing by ceramic fibre grinding wheel (Ra1.6μm), fine polishing by diamond grinding paste (Ra0.2μm).

Electrolytic polishing: Nitric acid-Hydrofluoric acid mixture (concentration 10%-15%), surface roughness reduced by 50%, corrosion resistance improved.

Laser polishing: through high-energy laser beam melting surface microscopic bumps, to achieve Ra0.1μm level mirror effect, precision control ±0.005mm.

2. Functional surface treatment

Anodising: Voltage 60V, generating 5-10μm oxide film, hardness HV800-1200, suitable for wear-resistant parts.

Sand blasting reinforcement: Al₂O₃ grit (particle size 0.2-0.5mm), surface compressive stress increased by 30%, fatigue life extended by 2 times.

Medical grade passivation: Nitric acid passivation (20%-30% concentration), eliminates free nickel ions, passes ISO 10993 biocompatibility test.

V. Industry Application and Cost Optimisation Cases

1. 3C electronic field

Case: A brand of mobile phone titanium alloy middle frame using TC4 ELI material, MIM forming + CNC finishing, mass production cost reduction of 40%, weight reduction of 15%.

2. aerospace field

Case: turbine blades through five-axis linkage machining, blade profile accuracy ± 0.005mm, temperature resistance increased to 800 ℃, fuel efficiency increased by 12%.

3. Medical device field

Case: orthopedic implants using Ti-13Nb-13Zr alloy, surface laser microporous treatment (pore size 50-200μm), bone integration cycle shortened by 30%.

VI. Industry Trends and Technological Innovations

1. Composite Processes of Powder Metallurgy and Additive Manufacturing

Technology Convergence: Titanium alloy powder injection moulding (MIM) combined with CNC finishing can create honeycomb sandwich or gradient pore structure, and the material utilisation rate is increased from 60% to 95%.

Case: A company uses MIM+CNC process to produce artificial vertebrae with controllable porosity of 300-500 μm and 40% increase in osseointegration efficiency.

2. Intelligent processing and real-time monitoring

AI process optimisation: cutting parameters are dynamically adjusted through machine learning, tool life is extended by 30%, and processing efficiency is increased by 20%.

Digital twin technology: build virtual machining model to prejudge tool wear, yield rate increased from 95% to 99.5%.

3. Green Manufacturing and Waste Recycling

Waste Recycling: Titanium alloy scrap is regenerated by hydrogenated dehydrogenation (HDH) process, with oxygen content ≤0.15%, and recycling rate of 80%.

Low-carbon machining: Micro quantity lubrication (MQL) technology replaces traditional cutting fluid, reducing carbon emissions by 60%.

If you have CNC machining needs, you can contact JLCCNC at any time, there will be a professional team to provide you with fast, economical and professional services.