How many kinds of surface treatment process of PM parts?

1. Coating: covering the surface of processed parts with a layer of other materials without any chemical reaction;
2. Surface chemical treatment: chemical reaction between the surface of processed parts and the added reactants;
3. Chemical heat treatment: other elements such as C and N diffuse to the surface of the parts to be treated;
4. Surface heat treatment: phase transformation occurs through the cyclic change of temperature, which changes the microstructure of the surface of the workpiece to be treated;
5. Mechanical deformation method: to make the surface of the workpiece to be processed produce mechanical deformation, mainly to produce compressive residual stress, but also to improve the surface density.
The above is about the surface treatment process of powder metallurgy parts. In principle, the surface treatment process applied to dense steel products can be used for iron-based powder metallurgy materials, but there are two prerequisites to consider. First of all, the dimensional tolerance of P / M parts with strong competitiveness can be maintained after treatment. If the surface treatment process used makes the P / M parts lose this advantage, it can not be applied. Secondly, due to the porosity of PM parts, this will have a significant impact on some existing surface treatments.