The Basic Guide for Titanium Injection

Titanium Metal Injection Molding (TiMIM) is a process that involves injecting titanium alloy into a metal mold to product products.
Titanium is a high-strength, corrosion-resistant metal. Products made from titanium alloys can be used in biological components, automotive parts, and aerospace components, among others. Compared to traditional methods of producing titanium alloys, the products produced by this process have higher density, more complex shapes, and lower production costs for large-scale manufacturing.

Metal Injection Molding (MIM) Process 

The production of titanium alloy injection molding is divided into four steps. Here is a detailed introduction to the process:

Raw Material Preparation

The first step is to mix ultrafine titanium metal powder with binder materials (a combination of thermoplastic plastics and wax binders) to form the feedstock. This feedstock is granulated for easy handling by injection molding equipment. The binder serves to give the metal powder a moldable shape and to maintain the shape of the powder during the initial stages of the process.

Molding

Next, the feedstock is heated and injected into the mold cavity under high pressure. This step can precisely produce extremely complex shapes. The parts formed at this stage are called “green” parts. Their geometric shape is identical to the final product, but they are about 20% larger than the final product to account for shrinkage during the subsequent sintering stage.

Debinding

After molding, the green parts undergo a debinding process to remove most of the binder material. This step is crucial for preparing the parts for sintering, as it removes the binder in a controlled manner, leaving behind a porous structure mainly composed of titanium powder. The parts at this stage are called “brown” parts.

Sintering

The final major step is sintering, where the brown parts are heated to a temperature near the melting point of titanium. This process eliminates the remaining binder and fuses the metal particles together, densifying the parts to achieve their final geometric shape and mechanical strength. The sintering process produces net-shaped, high-density parts with properties close to forged metals.

Physical and Chemical Characteristics of Titanium Alloys:

  • Density

MIM titanium parts, for example, those made from Ti-6Al-4V alloy, have a density of 4.20g/cm³. This process can enhance the strength and lifespan of the material.

  • Surface Finish

MIM parts have excellent surface finish, and this is also true for titanium alloy parts.

  • Alloy Composition

Titanium alloys are primarily composed of Ti-6Al-4V, which consists of 90% titanium, 6% aluminum, and 4% vanadium. This alloy composition balances strength, corrosion resistance, and biocompatibility.

  • Biocompatibility

For example, Ti-6Al-4V has high biocompatibility, making it suitable for medical implants and devices. Its corrosion resistance and performance in harsh bodily environments are particularly noteworthy.

  • Tensile Strength

The tensile strength of Ti-6Al-4V parts is ≥750Mpa.

  • Yield Strength

The yield strength of Ti-6Al-4V parts is ≥650Mpa.

  • Elongation

The elongation of Ti-6Al-4V can reach up to 10%.

  • Hardness

The hardness of MIM Ti-6Al-4V parts is about 30HRC.

Titanium Alloys Used in TiMIM

  • Ti-6Al-4V

This alloy, also known as Grade 5 titanium, is the most commonly used titanium alloy in the MIM process. It consists of titanium with 6% aluminum and 4% vanadium. Ti-6Al-4V is known for its high strength, lightweight, and excellent corrosion resistance. It is widely used in aerospace, medical, and automotive industries for components that require high performance and reliability.

Design Considerations for Titanium Injection Molding 

Titanium injection molding, being a part of Metal Injection Molding (MIM), requires consideration of key factors based on the provided information:

  1. Complex Part Production: To produce parts with complex geometry, it is common to break down complex parts into simpler components to reduce the difficulty of production.
  2. Wall Thickness Consistency: Maintaining consistent wall thickness can prevent defects caused by uneven shrinkage during production, reducing warping, dents, and voids.
  3. Ejection Angles: Generally, MIM products have small ejection angles. Increasing the ejection angle can facilitate the removal of the product from the mold.
  4. Shrinkage Compensation: Titanium alloy injection molding also involves product shrinkage. This is generally adjusted by modifying the mold to bring it closer to the final dimensions.
  5. Structural Integrity: It is desirable for the product structure to be complete, allowing parts
    to be sintered without additional support, which is beneficial for maintaining the integrity of the product shape.
  6. Surface Finish: Like other MIM parts, titanium alloy parts have excellent surface finish.
  7. Material Selection: Different titanium alloys have different properties, such as strength, corrosion resistance, and biocompatibility. The alloy should be selected based on the intended use of the part and the specific performance requirements of the application.
  8. Gate and Ejection System Design: The design of the gating system (including the channels through which molten material enters the mold) and the ejection system (which removes the part from the mold) is crucial for the quality of the final part. Correct positioning and design of gates and ejector pins affect the appearance, dimensional accuracy, and structural integrity of the part.
  9. Cost Considerations: Although titanium injection molding can reduce material waste and assembly costs, the initial investment in mold design and manufacturing can be significant. Designing for manufacturability and optimizing part design for the molding process can help reduce overall costs.

Limitations of Titanium Injection Molding 

While titanium injection molding offers numerous advantages due to its outstanding properties, there are some limitations, some of which are inherent to the product, while others are related to the process or cost:

High Cost

Titanium alloys are expensive raw materials. Although the injection process has enriched the utilization of titanium alloys, the initial investment in molds still poses challenges for widespread adoption.

High Injection Pressure

Titanium metal requires high injection pressure during the process, which can easily form flash in the mold. Maintaining precise pressure is a challenge.

Preventing Surface Oxidation

Titanium can react with certain gases during production or processing, leading to surface oxidation or embrittlement, which weakens the strength of the parts. Therefore, it is important to choose suitable equipment and coolants.

Work Hardening and Residual Stress

The internal structure of titanium alloys is not flexible, and they are prone to stress during processing. Therefore, it is advisable to minimize secondary machining when designing titanium alloy parts. Additionally, machining titanium alloys can lead to rapid tool wear.

Comparison with Other Manufacturing Methods 

Compared to other manufacturing methods, the cost of titanium injection molding (TiMIM) depends on several factors, including the complexity of the parts, production volume, and the amount of material waste generated. Here is a comparison based on the provided information:

  • Traditional Pressing and Sintering

The density of titanium injection molded parts is +99%, higher than the 88% typically achieved by traditional pressing and sintering methods. Although both methods have high tensile strength, elongation, and hardness, titanium injection molding can produce complex parts with better surface finish and is suitable for mass production. Compared to the low cost of traditional pressing and sintering, the cost of titanium injection molding is moderate.

  • Machining

Compared to traditional multi-axis machining, titanium injection molding can produce near-net-shape parts with minimal post-processing, saving a significant amount of cost. This greatly reduces material waste, as machining usually requires removing a large amount of material to achieve the final part geometry. Although machining provides 100% density and higher tensile strength, elongation, and hardness, its cost is higher and less suitable for mass production.

  • Investment Casting

Compared to investment casting, titanium injection molding can produce parts with higher complexity and better surface finish. The range of materials suitable for investment casting is medium to high, with medium production capability, while titanium injection molding has a broader range of suitable materials and is more suitable for mass production. The cost of titanium injection molding is moderate, while the cost of investment casting is also moderate.

  • 3D Printing 

The break-even point between the cost of 3D printing and injection molding is between 250 and 2000 parts. Although 3D printing has advantages in small batch production and allows for easy design changes without additional mold costs, injection molding becomes more cost-effective for large-scale production, as the cost of molds can be amortized over a large number of parts.

  • Polyurethane Casting

Polyurethane casting is more cost-effective than 3D printing at a certain production volume, but injection molding becomes more economical as production volume increases. Injection molding requires a higher initial mold manufacturing cost, but this cost is quickly amortized over a large number of parts produced.

TIMIM Applications

Biomedical Applications

In biomedicine, the most commonly used titanium alloy is Ti-6Al-4V, which has corrosion resistance and high biocompatibility. It typically follows the ASTM F2885 standard, ensuring that the material meets requirements in terms of density, chemical properties, and mechanical properties.

Automotive Industry 

Titanium alloys are used in motorcycles and cars due to their light weight and high strength. The emergence of the TiMIM process has allowed for better utilization of this precious metal, leading to increased use in the automotive industry.

Aerospace Industry 

The high strength and good corrosion resistance of titanium alloys make them highly suitable for aerospace applications, especially in engine and spacecraft structural materials. Their excellent mechanical properties and high-temperature resistance can help reduce the weight of spacecraft.

Conclusion

We hope this guide has given you insight into the basic information about the TiMIM.
For TiMIM parts from China, contact us now.

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