ASTM B923

Metal Powder Skeletal Density by Helium or Nitrogen Pycnometry

Applicability: ASTM B923 applies to metal powders and particulate materials including elemental powders, pre-alloyed powders, cermets, carbides, nitrides, and metal oxides used in powder metallurgy, additive manufacturing, thermal spray, and hard-facing applications. It is applicable to powders that are chemically inert to helium or nitrogen displacement gases; materials that react with these gases or that cannot be degassed of chemisorbed species require alternative density measurement methods. The method applies to powders with particle sizes typically ranging from sub-micron to several millimeters.

Purpose: ASTM B923 determines the skeletal (true) density of metal powder by measuring the volume displaced by a known mass of powder using a gas pycnometer with either helium or nitrogen as the displacement medium, excluding interparticle void volume and any internal porosity within individual particles. Skeletal density data are used to characterize material purity, verify alloy composition, and calculate theoretical density and porosity of sintered or deposited coatings, and they support quality control in additive manufacturing and conventional powder metallurgy processes where precise material density is critical to achieving target mechanical properties.