Page 150 - Module DMV20173

8.0 POWDER PROCESSING

9.2.2 BLENDING METAL POWDERS

1. Blending refers to when the powders of the same chemical composition but possibly
different particle size are intermingled.
2. Different particle are blended to reduce porosity.

3. Mixing refers to powders of different chemistries being combined.
4. An advantage of PM technology is the opportunity to mix various metals into alloys
that would be difficult or impossible to produce by other process.
5. The process accomplished by mechanical means such as, rotation in drum, rotation

in a double-cone container, agitation in a screw mixer and stirring in a blade mixer
(Figure 8.4).
6. To achieve best result in mixing, the container will be filled between 20% - 40% full.

7. The containers are usually designed with internal baffles or other ways of preventing
free-fall during blending of different size of powder, because variations in settling
rates between sizes result in segregation.

8. Other ingredients are added during blending or mixing process:

a. Lubricant, zinc and aluminum is added in small amounts as to reduce friction
between particles and at the die wall during compaction.
b. Binder, which are required in some cases to achieve adequate strength in the
pressed but unsintered part.
c. Deflocculants, which inhibit agglomeration of powder for better flow

characteristics during subsequent processing.

Figure 8.4 Mixing and blending processes of metal powders. (a) crushing (b) mixing (c)
hammering.

BPLK 182 DMV 20173