Grey iron powder/Pure iron metal powder:

 Iron powder including Reduced iron powder, Automazied iron powder,Casting iron powder & electrolitic iron powder.

for friction materials application, it should be sponge iron powder.   Spec as follow:

Purity: Fe98.5% Min;  Bulk density: 2.2-3.0g/cm3;   Size:80-325 mesh;

Sponge Iron powder has smaller density than reduced iron powder, efficiently help semi-metal friction products lower braking noise by its porous structure.

and also Pure iron powder used on P/M Parts, Welding Rod, Warmer pad, Chemical reductant...Spec is upon your request.