Analysis of surface treatment technology of mechanical turned parts for the medical sector

Mechanical turned parts for the medical sector are widely used in surgical instruments, implants, medical equipment and other fields. These parts not only need to meet strict dimensional tolerance requirements, but also need to have excellent surface quality to ensure stability and durability in the biological environment.

High-quality surface treatment can not only improve the corrosion resistance, wear resistance and biocompatibility of parts, but also effectively reduce friction, reduce tissue damage, and improve patient safety and comfort. This article will deeply analyze the surface treatment technology of mechanical turned parts for the medical sector, introduce common treatment methods, industry standards and their key roles.

1. Materials and surface treatment requirements of mechanical turned parts for the medical sector

The material selection of mechanical turned parts for the medical sector needs to be carefully considered, and the selection of suitable materials and corresponding surface treatment methods is crucial.

(1) Common materials

1) Stainless steel (316L):

It has good corrosion resistance and mechanical strength and is widely used in surgical instruments and orthopedic implants.

2) Titanium alloy (Ti-6Al-4V):

It is light in weight and has good biocompatibility. It is often used in artificial joints and dental implants.

3) Cobalt-chromium alloy:

High hardness and strong wear resistance, suitable for artificial hip and knee joints.

4) PEEK (polyetheretherketone):

High strength, low density, fatigue resistance, often used in spinal implants.

(2) Surface performance requirements

1) Corrosion resistance:

Avoid oxidation or degradation in body fluid environment.

2) Biocompatibility:

Ensure that the material does not cause human immune rejection or inflammatory response.

3) Wear resistance:

Reduce wear caused by long-term use and increase part life.

4) Low friction:

Reduce joint friction, reduce tissue damage, and improve patient comfort.

5) Surface finish:

Machining residue (burrs, microcracks), so surface treatment is needed to reduce the risk of bacterial attachment and improve the bone integration ability of implants.

2. Common surface treatment technologies for mechanical turned parts for the medical sector

Mechanical turned parts for the medical sector usually use a variety of surface treatment technologies to meet different usage requirements.

(1) Mechanical treatment methods

1) Polishing (mechanical polishing, electrolytic polishing)

- Mechanical polishing removes surface roughness and improves smoothness through grinding and polishing tools.

- Electrolytic polishing uses electrochemical reactions to remove tiny burrs on the surface, making the surface smoother and improving corrosion resistance.

● Application: surgical instruments, cardiovascular stents, and artificial joint surface treatment.

2) Sandblasting

- Alumina, glass beads or ceramic particles are sprayed through high-pressure airflow to remove the oxide layer and improve surface roughness.

- Improve bone integration ability and promote the combination of implants and bone tissue.

● Application: dental implants, hip joints, bone fixation plates.

(2) Chemical and electrochemical treatment

1) Electrolytic polishing

- Anodic dissolution is used to remove tiny surface protrusions and improve smoothness.

- Reduce surface friction coefficient, improve corrosion resistance, and prevent bacterial attachment.

● Application: cardiovascular stents, orthopedic implants.

2) Passivation treatment

- Stainless steel is treated with nitric acid or citric acid to remove free iron on the surface and form a protective oxide layer.

- Enhanced corrosion resistance, especially suitable for humid and body fluid environments.

● Applications: surgical tools, implantable fixation screws.

(3) Coating technology

1) PVD (physical vapor deposition) / CVD (chemical vapor deposition)

- Form a hard, wear-resistant ceramic coating on the surface of the part to improve corrosion resistance and biocompatibility.

- PVD is suitable for stainless steel and titanium alloys to enhance surface hardness.

- CVD can be used in ultra-high temperature environments, such as cobalt-chromium alloy implants.

● Applications: surgical blades, orthopedic implants, dental implants.

2) DLC (diamond-like carbon coating)

- Has extremely low friction coefficient and high wear resistance.

- Can reduce wear on the implant surface and reduce tissue inflammatory response.

● Applications: artificial joints, cardiovascular stents, surgical instruments.

3) Ceramic coating

- Use zirconium oxide or hydroxyapatite (HA) for surface coating to improve corrosion resistance and biocompatibility.

- HA coating helps bone tissue bonding and is suitable for orthopedic implants.

● Application: artificial hip joint, dental implant.

(4) Surface modification technology

1) Laser surface treatment

- Laser heating the surface changes the microstructure of the material, improves hardness and wear resistance.

- Can be used for microstructure modification and improve bone integration ability.

● Application: orthopedic implants, surgical tools.

2) Plasma spraying

- Plasma is used to spray high melting point materials onto the surface of parts to form a high hardness and wear-resistant layer.

- Commonly used in titanium alloy implants to improve bone integration ability.

● Application: artificial hip joint, knee joint implant.

3. Surface treatment standards and testing of mechanical turned parts for the medical sector

The medical industry has strict standards for the quality of surface treatment of mechanical turning parts to ensure product safety and consistency.

(1) ISO 10993 (biocompatibility standard)

Specifies that materials must undergo cytotoxicity, sensitization and inflammatory response tests to ensure harmlessness.

(2) ASTM F86 (Surface Treatment Standard for Titanium and Titanium Alloys)

Specifies the surface cleaning and treatment process of titanium alloy implants.

(3) Surface roughness test (Ra value requirement) 

Generally, Ra < 0.2 μm is required to reduce bacterial adhesion and improve smoothness.

(4) Corrosion resistance test

- Salt spray test: Test the oxidation resistance of stainless steel and titanium alloys.

- Electrochemical corrosion test**: Evaluate the corrosion resistance of materials under physiological environment.

4. Conclusion

The surface treatment technology of mechanical turned parts for the medical sector is the key to ensure the durability, stability and biocompatibility of parts. Different materials require corresponding surface treatment processes to optimize their performance.