Metal Powder Industries Releases Publication on Metal AM Powder Standards

“A Collection of Powder Characterization Standards for Metal Additive Manufacturing,” Metal Powder Industries Federation’s (MPIF’s) recent publication, contains nine existing MPIF standard test methods that can be applicable for the characterization of powders used in metal additive manufacturing (AM) processes with an explanation of each standard. These standards relate to those activities that concern designers, manufacturers and users of metal AM parts.

Including MPIF characterization standards one to five, 28, 46, 48 and 53, the collection describes the scope of the standard or what it means, the purpose of the standard, and its relevance to metal AM.

• Standard 01—the Method for Sampling Metal Powders—describes methods for sampling packaged powders or powders in the process of being packaged. Its purpose is to establish an agreed-upon, industry-wide method for obtaining samples needed for powder suitability testing. This standard describes how this is accomplished for both in-process and packaged material.
• Standard 02—Method for Determination of Loss of Mass in a Reducing Atmosphere for Metal Powders (Hydrogen Loss)—describes how to determine loss of mass for metal powder and can indicate the purity of powder with regards to interstitial elements, which can affect the process and subsequent material properties negatively.
• Standard 03—Method for Determination of Flow Rate of Free-Flowing Metal Powders Using the Hall Apparatus—describes how to determine how well powder will flow by using a standardized funnel. If the powder flows through the funnel, it indicates it will flow in other conditions, such as during a metal AM process where the powder is spread in a thin layer with minimal force.
• Standard 04—Method for Determination of Apparent Density of Free-Flowing Metal Powders Using the Hall Apparatus—helps to determine the apparent density of a powder when the powder is flowing freely under the force of gravity only (i.e. no outside energy or force is added to change the void space between particles). It measures how well a powder packs after flowing through a funnel, testing to reduce the void space between powder particles during powder spreading.
• Standard 05—Method for Determination of Sieve Analysis of Metal Powders—assesses the particle-size distribution of a powder lot by having the powder pass through a series of screens with progressively smaller openings, and weighing the material left on each screen. It recommends measuring powder sizes directly, as particle-size distribution can have a profound affect on thickness and densification in sintering for certain metal AM processes.
• Standard 28—Method for Determination of Apparent Density of Non-Free-Flowing Metal Powders Using the Carney Apparatus—determines the apparent density of a powder when it doesn't flow freely under the sole force of gravity and measures how well a non-free-flowing powder packs after passing through a funnel which has a larger orifice size than the funnel used in MPIF Standard 04. It is used primarily for smaller particle sizes. The technique in this standard allows the apparent density to be determined when the powder does not flow freely.
• Standard 46—Method for Determination of Tap Density of Metal Powders—determines the maximum density of a powder when vibrated under certain conditions as well as how well a powder packs when subjected to a vibrational force, as opposed to apparent density tests where powder packing is accomplished with minimal input energy. A high relative tap density value should be helpful for powder spreadability and uniformity during the metal AM process.
• Standard 48—Method for Determination of Apparent Density of Metal Powders Using the Arnold Apparatus—determines the apparent density of a powder using an alternative method from MPIF Standard 04 or 28 and measures how well a powder packs when it drops into a larger cylinder. This will typically be used for powders that do not flow freely.
• Standard 53—Method for Measuring the Volume of the Apparent Density Cup Used with the Hall and Carney Apparatus (Standards 04 and 28)—determines the volume of the cup used to determine apparent density in Standards 04 and 28. This procedure is a check to make sure that the volume of a cup in use is acceptably accurate, as over time it may change (i.e. worn edge of the cup). If Standards 04 or 28 are in use, then this Standard is necessary for ensuring ongoing accuracy of their results.

The publication features QR codes and hyperlinks for viewing educational video clip demonstrations of the working mechanics of the cited test methods. Both printed and PDF editions are available through the MPIF Publications Portal.