The powder compact is contacted with liquid metal or immersed in the liquid metal, the pores in the compact are filled with liquid metal, and the compact material or parts is obtained by cooling down. This process is called immersion. The immersion process relies on the external molten metal to wet the powder porous body. Under the action of capillary force, the liquid metal flows along the pores between the particles or the pores within the particles until the pores are completely filled.
The advantages of copper infiltration of powder metallurgy iron-based materials:
1. Improve mechanical properties;
2. Improve electroplating performance;
3. Improve brazing performance;
4. Improve machining performance;
5. Improve electrical and thermal conductivity;
6. Easy to control the size of parts;
7. Have good pressure sealing performance;
8. Multiple components can be combined;
9. Improve quenching quality;
10. Local infiltration of special parts requiring strengthening and hardening properties.
Influence factors：
1. Skeleton density
As the skeleton density increases, the strength of the copper-infiltrated sintered steel increases significantly, and the hardness also increases. This is due to the increase in the skeleton density, the increase in the amount of pearlite, and the relatively low copper content. In terms of cost, choosing a higher skeleton density can reduce the copper content, thereby improving economic benefits.
2. Add element Sn
The addition of low melting point element Sn is beneficial to increase the density and strength of copper-infiltrated sintered steel. From the Cu-Sn alloy phase diagram, it can be seen that copper alloys containing Sn have a lower liquid phase formation temperature, which can promote the smooth infiltration of copper alloys.
3. Temperature
As the temperature increases, the rate of grain expansion also increases, which is detrimental to improving the strength. Therefore, proper sintering-infiltration and holding time should be selected under the premise of ensuring the full alloying and homogenization of Fe-C, full infiltration of Cu, and full solid solution strengthening of Fe-Cu.