Against the background of the rapid development of modern medical technology, the selection and application of biomedical materials have a vital impact on medical effects and patient health. Titanium and titanium alloys have become one of the most widely used metal materials in the medical field due to their unique physical, chemical and biological properties. From orthopedic implants to oral repair materials, from heart stents to surgical instruments, titanium materials are everywhere. It not only solves the problems of poor durability and insufficient biocompatibility of traditional materials in the human body environment, but also provides a material basis for the innovation and breakthrough of medical technology. Wstitanium has a deep understanding of the application of titanium in the medical field, which is of great significance to promote the development of medical technology and improve the quality of life of patients.
1. Advantages of titanium in medicine
1.1 Excellent biocompatibility
Titanium can quickly form a dense oxide film (TiO₂) in the human body environment. This oxide film has good chemical stability, is not easy to react chemically with human tissues, and will not cause immune rejection. When in contact with human cells, the chemically active groups on the surface of the oxide film can interact with the extracellular matrix, promote cell adhesion, proliferation and differentiation, and create favorable conditions for tissue repair and regeneration. Studies have shown that osteoblasts can better attach and grow on the titanium surface, secrete bone matrix, and accelerate the bone integration process, which makes titanium have significant advantages in the field of orthopedic implants.
1.2 Good mechanical properties
The density of titanium is about 4.51g/cm³, which is only 60% of stainless steel, but its strength is comparable to that of high-strength alloy steel. Its tensile strength can reach more than 900MPa, which has extremely high specific strength. This characteristic enables titanium medical implants to effectively reduce weight and reduce the burden on the patient’s body while meeting the mechanical support needs of the human body. In addition, the elastic modulus of titanium alloy (about 100-120GPa) is relatively closer to human bones (about 10-40GPa). Compared with traditional stainless steel (elastic modulus of about 200GPa) and cobalt-chromium alloy (elastic modulus of about 210GPa), it can reduce the stress shielding effect and avoid bone absorption and bone atrophy caused by the large difference in elastic modulus between implants and bones.
1.3 Excellent corrosion resistance
The human body environment is complex, containing a variety of electrolyte solutions, enzymes, proteins and other components, which puts strict requirements on the corrosion resistance of implant materials. The oxide film on the surface of titanium can effectively resist the corrosion of human body fluids. Even when it is mechanically damaged, it can quickly regenerate a new oxide film to maintain the stability of the material. During long-term implantation, titanium will not be corroded and dissolved to produce metal ions, avoiding the toxic effects of metal ions on human tissues and organs, ensuring the long-term safety and effectiveness of implants.
1.4 Good machining performance
Titanium and titanium alloys can be made into medical products of different shapes and structures through a variety of machining techniques. Whether it is traditional mechanical machining (such as CNC machining) or advanced additive manufacturing (such as 3D printing), it can achieve precise machining of titanium materials to meet the medical field’s demand for personalized and high-precision products. In addition, titanium materials can also be further improved through surface treatment technologies (such as micro-arc oxidation, laser machining, etc.) to improve their surface properties, enhance biological activity and wear resistance, and improve the overall performance of products.
2. CNC machining of titanium parts
2.1 Tool selection
When CNC machining titanium parts, the choice of tool directly affects the machining quality and efficiency. Since titanium alloys have high hardness, high cutting temperature, and are easy to bond with tools, the tool material must have high hardness, high wear resistance, and good heat resistance. Carbide tools are a common choice, among which tungsten-cobalt (YG) carbide tools, such as YG8 and YG6X, are suitable for rough machining due to their good toughness and wear resistance; grades such as YG3X with lower cobalt content and higher hardness are suitable for fine machining. In addition, coated tools (such as TiAlN and TiCN coatings) can significantly improve the cutting performance of tools, reduce cutting temperatures, and reduce tool wear.
The design of tool geometry parameters is also crucial. The rake angle is generally small (5° – 10°) to enhance the blade strength; the back angle is 8° – 12° to reduce the friction between the back face of the tool and the workpiece; the helix angle is selected from 30° – 45° to improve the stability of the cutting process; the radius of the blunt circle of the cutting edge is controlled at 0.05 – 0.1mm to balance the blade strength and cutting resistance.
2.2 Cutting parameter optimization
The reasonable selection of cutting speed, feed rate and cutting depth is the key to CNC machining of titanium parts. Due to the poor thermal conductivity of titanium alloy, excessive cutting speed will cause the cutting temperature to rise sharply and accelerate tool wear. Therefore, the cutting speed is usually controlled at 50 – 100m/min during rough machining and 30 – 80m/min during fine machining. The feed rate must take into account both machining efficiency and surface quality. It can be 0.1 – 0.3mm/z during rough machining and 0.05 – 0.15mm/z during fine machining. The cutting depth is determined according to the machining allowance of the part and the strength of the tool. It can reach 1/3 – 1/2 of the tool diameter during rough machining, and is generally 0.1 – 0.5mm during fine machining.
2.3 Key points of machining technology
When CNC machining titanium parts, the clamping method has an important influence on the machining accuracy. Special fixtures or hydraulic fixtures are required to ensure that the clamping is firm and does not cause deformation, while avoiding excessive local stress on the workpiece due to concentrated clamping force. In terms of cooling and lubrication, a high-pressure and high-flow special cutting fluid (pressure 3 – 10MPa, flow 20 – 50L/min) is used to spray directly into the cutting area to take away heat and reduce friction between the tool and the workpiece. In addition, during the machining process, it is necessary to monitor the cutting force, temperature and other parameters in real time, adjust the cutting parameters in time, and prevent tool damage and part deformation.
3. 3D printing titanium parts
3.1 Principles and classification of 3D printing technology
The 3D printing technologies used for titanium parts manufacturing mainly include selective laser melting (SLM), electron beam melting (EBM), etc. Selective laser melting technology uses a high-energy laser beam to melt titanium alloy powder layer by layer, and forms it according to a pre-designed three-dimensional model. It has the characteristics of high forming accuracy and good surface quality, and is suitable for manufacturing medical implants with complex structures. Electron beam melting technology uses an electron beam as a heat source to melt titanium alloy powder in a high vacuum environment. It has high machining efficiency, fast forming speed, and can effectively reduce internal defects of the material. It is suitable for manufacturing large orthopedic implants.
3.2 Advantages of 3D printed titanium parts
Compared with traditional machining methods, 3D printed titanium parts have significant advantages. First, it can realize the direct forming of complex structures, such as porous structures and bionic structures. These structures can imitate the microstructure of human bones, promote the growth of bone tissue, and enhance the combination of implants and human tissues. Secondly, 3D printing supports personalized customization. According to the patient’s CT or MRI data, implants that fully fit the patient’s anatomical structure can be designed and manufactured to improve the success rate of surgery and the patient’s postoperative comfort. In addition, 3D printing can also reduce material waste, improve material utilization, and reduce production costs.
3.3 Challenges and Solutions of 3D Printed Titanium Parts
Although 3D printed titanium parts have many advantages, they also face some challenges. For example, residual stress and deformation are easily generated during the printing process, which affects the dimensional accuracy and mechanical properties of the parts; the surface roughness after printing is high and requires subsequent machining. To address these problems, residual stress and deformation can be reduced by optimizing printing process parameters (such as laser power, scanning speed, layer thickness, etc.), adopting support structure design, and performing heat treatment (such as annealing, aging treatment). For surface quality issues, post-machining processes such as mechanical machining, chemical polishing, and electrochemical polishing can be combined to improve the surface finish of parts.
4. Application of Titanium in the Medical Field
4.1 Orthopedic Implants
Artificial joints: Titanium alloys are the main materials for manufacturing artificial hip joints, knee joints, shoulder joints, etc. Artificial joints need to bear the weight and movement load of the human body for a long time. The high strength and good wear resistance of titanium alloys can ensure the service life of the joints. Its porous structure design can also promote bone tissue ingrowth, achieve a firm combination of implants and human bones, and reduce the risk of loosening and dislocation.
Bone fixation devices: including bone plates, screws, intramedullary nails, etc., used for fracture reduction and fixation. Titanium bone fixation devices have good biocompatibility and mechanical properties, and can provide a stable support environment for fracture healing. Some bone plates use degradable coating technology, and the coating gradually degrades after the fracture heals, reducing long-term stimulation to human tissue.
4.2 Oral restoration materials
Dental implants: Titanium has become the preferred material for dental implants due to its excellent biocompatibility and bone integration ability. After the implant is implanted in the alveolar bone, it can form a tight bone integration with the bone tissue and provide a stable support for the crown. The application of surface treatment technology (such as sandblasting, acid etching, anodizing, etc.) further improves the surface activity of titanium implants and accelerates the bone integration process.
Dental bracket: Titanium alloy denture bracket has the characteristics of light weight, high strength and corrosion resistance, and can provide good support and retention for dentures. Its elastic modulus is close to that of human bones, which is more comfortable to wear, and does not produce metallic odor and allergic reactions like traditional metal brackets.
4.3 Cardiovascular interventional devices
Heart stents: Titanium alloys can be used to manufacture heart stents. Their good biocompatibility and corrosion resistance can reduce thrombosis and inflammatory reactions after stent implantation. Some titanium alloy stents use drug coating technology to slowly release drugs after stent implantation, inhibit vascular intimal hyperplasia, and reduce the incidence of restenosis.
Heart valves: Although heart valves are currently mainly made of biomaterials and metal alloys (such as cobalt-chromium alloys), titanium alloys have also shown potential application prospects in the field of heart valves due to their excellent comprehensive performance.
4.4 Surgical instruments
Titanium alloy surgical instruments (such as scalpels, tweezers, scissors, etc.) are light in weight, high in strength, and corrosion-resistant, which can improve the flexibility and accuracy of surgical operations. Its non-magnetic properties make it suitable for surgery guided by magnetic resonance imaging (MRI), avoiding the interference of traditional metal instruments on imaging quality. In addition, the surface of titanium alloy instruments is smooth, not easy to adhere to tissues and blood, easy to clean and disinfect, and reduce the risk of infection.
5. Summary
Titanium and titanium alloys have shown great application value in the medical field due to their excellent biocompatibility, good mechanical properties, excellent corrosion resistance and good machining performance. CNC machining technology and 3D printing technology provide a variety of means for the manufacture of titanium parts, meeting the high-precision and personalized needs of medical products. From orthopedic implants to oral repair materials, from cardiovascular interventional devices to surgical instruments, the application of titanium materials has significantly improved the medical level and improved the quality of life of patients.
With the continuous development of medical technology and the growing demand for health, higher requirements are also placed on titanium materials and their machining technology. In the future, it is necessary to further optimize the composition design and machining technology of titanium alloys, and develop new titanium alloy materials with better bioactivity, mechanical properties and degradation properties. At the same time, combined with advanced technologies such as artificial intelligence and big data, the intelligent design and manufacturing of titanium medical products can be realized, and the development of personalized medicine can be promoted. In addition, strengthening basic research and in-depth exploration of the interaction mechanism between titanium materials and human tissues will open up broader prospects for the application of titanium in the medical field and make greater contributions to human health.
