Common Surface Treatment Processes for Metal Injection Molding (MIM) Parts

Common Surface Treatment Processes for Metal Injection Molding (MIM) Parts

In today's society, products in fields such as automobiles, aerospace, the military, and consumer electronics (like mobile phones, watches, medical devices, home appliances, cameras, etc.) are closely connected to our daily lives. And the Metal Injection Molding (MIM) technology plays an important role in these industries. Next, let's learn about several common surface treatment processes for MIM parts.

I. Overview of Metal Injection Molding (MIM)

Metal Injection Molding (MIM) is a process that combines metal powders and binders and goes through a series of processing steps to manufacture metal parts.

Basic steps:

1. Mix metal powders with binders.

2. Granulate the mixture.

3. Inject the granulated materials into molds to form the desired shapes.

4. Conduct debinding and sintering to obtain the final parts.

The advantage of the MIM process is that it combines the high design flexibility of injection molding with the high strength and high precision of metal materials, enabling the low-cost manufacturing of parts with complex geometries. This process is generally divided into four main steps: mixing, molding, debinding, and sintering. Whether surface treatment is needed depends on the specific application requirements and performance requirements of the parts.

 II. Common Surface Treatment Processes for MIM Parts

(A) Polishing Treatment

Polishing treatment uses mechanical, chemical or electrochemical methods to make the surface of the workpiece smoother and reduce the surface roughness. This has many benefits, such as making the parts look more attractive and reducing friction and wear. In some places where high surface finish is required, such as medical devices and precision tools, polishing treatment is essential.

(B) Electroplating Treatment

Electroplating is a process of attaching a metal film to the surface of metals or other materials through electrolysis. Electroplating has many functions, such as preventing metals from rusting, improving wear resistance, electrical conductivity and reflectivity, and making the parts more aesthetically pleasing. Common electroplating materials include nickel, gold, chromium, and copper. Electroplating treatment is widely used in fields such as automobiles, electronics, decoration, and precision engineering, especially for MIM parts that need to improve corrosion resistance, wear resistance and appearance quality.

(C) Physical Vapor Deposition (PVD) Treatment

PVD transfers atoms or molecules of materials from one place to the surface of parts through a physical process. It can deposit a coating with special properties on substrates with relatively poor performance, such as improving the hardness, wear resistance, thermal conductivity and corrosion resistance of the part surface. PVD treatment is widely used on components with high wear resistance requirements, such as cutting tools, molds, and aerospace parts.

(D) Blackening Treatment

Blackening treatment forms a black oxide film on the metal surface through a chemical reaction. This oxide film can isolate the air and prevent the metal from rusting, having a certain anti-corrosion effect. Generally, blackening treatment is used on parts that do not have high appearance requirements but need corrosion prevention, such as military, automotive and industrial parts. The main components of the blackening solution are sodium hydroxide and sodium nitrite.

(E) Phosphating Treatment

Phosphating treatment forms a phosphate film on the metal surface through chemical or electrochemical reactions. The main functions of phosphating are as follows:

1. Corrosion protection: The phosphate film can prevent low-cost metal materials from being corrosed.

2. Improving coating adhesion: It can make paints and other coatings adhere better to the metal surface, enhancing the anti-corrosion performance and durability of the coatings. Phosphating treatment is widely used in industries such as automobiles, mechanical equipment, and home appliances, especially for parts that need corrosion prevention and coating adhesion.

(F) Spraying Treatment

Spraying treatment evenly sprays liquid or powder coatings onto the surface of MIM parts with the help of pressure or centrifugal force. Spraying has many functions, such as providing thermal protection, corrosion resistance and electrical insulation. Spraying treatment is generally used on relatively large MIM parts, especially for industrial parts and equipment that require high durability or special functional coatings.

III. Summary

Polishing and phosphating treatments are mainly preparations for other post-treatments and can improve surface quality and coating adhesion. Electroplating and PVD are two common treatment technologies, suitable for MIM parts that require improvement in corrosion resistance, wear resistance and aesthetics. Blackening and spraying can significantly change the surface characteristics of parts and are especially suitable for large parts and applications with special surface functional requirements.

Selecting appropriate surface treatment processes is very important for improving the performance and appearance of MIM parts. It should be comprehensively considered according to the specific application requirements, functional requirements and cost-effectiveness of the parts. Through these surface treatment technologies, the mechanical properties, durability and appearance of MIM parts can be greatly improved, thus being widely used in multiple fields such as aerospace, automobiles, electronics, and medical treatment.