Surface Treatment Process of Powder Metallurgy Parts

The metal injection molding process can manufacture precision parts and components with strict tolerances of ±0.025 mm and fine details. However, parts made with CNC milling machines usually have obvious marks. Therefore, surface treatment is a core part of the manufacturing process because it helps to improve the aesthetics, corrosion resistance and wear resistance of different CNC machined metal parts.

01 Surface treatment process of powder metallurgy parts
Powder metallurgy is a process technology for preparing metal powder or using metal powder as raw material, forming and sintering, and manufacturing metal materials, composite materials and various types of products. In order to improve the wear resistance, corrosion resistance and fatigue strength of powder metallurgy parts, powder metallurgy parts must be surface treated to make its surface more functional and denser.

So, what is the surface treatment process of powder metallurgy parts?
The surface treatment process of powder metallurgy parts can basically be divided into the following five categories:
1. Coating: Covering a layer of other materials on the surface of the treated part without any chemical reaction;
2. Surface chemical treatment: Chemical reaction between the surface of the treated part and the added reactant;
3. Chemical heat treatment: Other elements such as C and N diffuse into the surface of the treated part;
4. Surface heat treatment: Phase change occurs through temperature cycle changes, causing changes in the microstructure of the surface of the treated part;
5. Mechanical deformation method: The surface of the treated part is deformed, mainly to produce compressive residual stress and also increase the surface density. The above is the introduction of the surface treatment process of powder metallurgy parts. In principle, all surface treatment processes applied to dense steel products can be used for iron-based powder metallurgy materials, but there are two prerequisites that must be considered. The first is that after treatment, the precise dimensional tolerance that can maintain the advantage of powder metallurgy parts with strong competitiveness can be maintained. If the surface treatment process used makes the powder metallurgy parts lose this advantage, it cannot be used. Secondly, since powder metallurgy parts contain pores, this will have a significant impact on some existing surface treatments.

02 Surface rust prevention methods for powder metallurgy products

1. Use anti-rust oil. Anti-rust paper for rust prevention After the powder metallurgy parts are processed, apply appropriate anti-rust oil and use anti-rust paper to package for rust prevention. During transportation and storage, in order to avoid rusting of the product, it must be kept in a sealed state and cannot be exposed to moisture. The use of anti-rust oil has certain requirements for storage and transportation! To ensure the anti-rust effect, the workpiece will not rust
2. Passivation and coating treatment Passivation and coating treatment, rust prevention is still required during transportation, and the coating has an impact on the later assembly and use. The anti-rust effect of this method is general, and the anti-rust time is not very long. If the anti-rust requirements are strict, it is possible to apply anti-rust oil for rust prevention
3. Use antioxidants for surface rust prevention methods such as iron-based powder metallurgy products. Antioxidants can be used. After stirring or shaking the solution evenly before use, immerse or spray it on the metal surface and dry it (dry).