Mechanical grinding of MIM materials

Whether it is hard and brittle or soft and tough materials, their grinding is extremely important for powder metallurgy processes and has important economic significance. For the manufacture of hard metal and oxide powders, the most widely used pulverization method is mechanical crushing. Supplementary grinding of oxide-reduced sponges, atomized powders or electrolytic powders is the most commonly used grinding method, and both hammer and rod grinders are used for this type of grinding. Depending on the material, the sintered material is either restored to the original particle size distribution during grinding, or is made into larger aggregates.

 

Mechanical crushing is limited to: harder, brittle metals (e.g., electrolytic iron and bismuth), certain active metals (e.g., glass and metal hydrides), ductile metals for the production of sheet metal particles, and chemically brittle materials (e.g., sensitized stainless steel).

 

The growing interest in finer metal powders produced by atomization has brought renewed attention to grinding, especially solid-state alloying or high-energy ball milling. However, the grinding of metal powder has not yet caused injection. The research carried out in the field of metal milling is essentially proprietary and empirical, and is therefore limited to special applications of powder metallurgy. The purpose of grinding is to:

 

1) Reduce particle size (crush or grind);

2) Increase particle size;

3) Change shape (sheet);

4) Reunion;

5) Solid state alloying (mechanical alloying);

6) Solid mixture (incomplete alloying);

7) Modify or change the properties of the material (density, fluidity or work hardening);

8) Properties of two or more materials (density, fluidity or work hardening);

9) Unbalanced processing of metastable phases (such as amorphous alloys, extended solid solutions and nanocrystalline structures).