The rate and uniformity of die cavity filling are related to flow properties, which thus influence production rates and uniformity of compacted parts.

The ability of a powder to flow is a function of interparticle friction. As interparticle friction increases, flow is slowed. Some powders, often fine powders and lubricated powder mixtures, may not flow through the Hall funnel of Test Method B 213.. Nevertheless, if a larger orifice is provided, such as in the Carney funnel, a meaningful flow rate may be determined, providing specific information for certain applications.

Test Method B 213., using the Hall funnel, is the preferred method for determining the flowability of metal powders. The Carney funnel of these test methods should only be used when a powder will not flow through the Hall funnel. These test methods may also be used for comparison of several powders when some flow through the Hall funnel and some do not.

Humidity and moisture content influence flow rate. Wet or moist powders may not flow through either the Hall or the Carney funnel.

These test methods are based on flow of a specific mass of powder. If flow of a specific volume of powder is preferred, Test Method B 855 may be used for powders that flow readily through the Hall funnel.

These test methods may be part of the purchase agreement between powder suppliers and powder metallurgy (PM) part producers, or it can be an internal quality control test by either the supplier or the end user.