ASTM F3606-22

SIGNIFICANCE AND USE 5.1 This guide will help manufacturers and users of AM powder feedstocks to identify suitable methods for measuring moisture in the feedstocks. 5.2 This guide will aid control of powder quality and allow powder producers and users of AM machines to assess moisture content of virgin and reused powders. 5.3 This guide is intended to support acceptance and control tests. 5.4 Moisture levels are usually relatively low in metallic powder feedstocks (typically lower than 250 µg/g) but could be significantly more important in polymer and ceramic (typically lower than 10 000 µg/g). 5.5 Moisture may affect powder processability (powder supply and feeding, layer creation) and influence the process and properties of the printed components. As different processes and machines use powders with different characteristics (that is, particle size distribution and shape) and AM machines store and handle powders in different ways, the amount of moisture and its impact may vary significantly depending on the feedstock, process, and machine. 5.6 A proportion of the water is physisorbed on the surface and can be easily adsorbed and desorbed. 5.7 A fraction of the water can be strongly bonded to the surface of the powder (that is, chemisorbed) and can be difficult to extract even at temperatures significantly higher than 100 °C. Thus, the water may not all be recovered during the moisture analysis and some water may remain in the samples. Consequently, the values obtained during the tests may be underestimated. As water bonds differently to different materials, the evaporation of water as a function of temperature may vary from one material to another. 5.8 Because of the reactive nature of powders, water may react with the surface of the powder and form oxides and hydroxides. Thus, the amount of moisture may change with time even if the powder is stored in a tightly sealed container. Reaction of the powder with water may also happen during the analysis as the powder i... SCOPE 1.1 This standard provides guidelines for measuring moisture in powder feedstock used in additive manufacturing (AM). It applies to metallic, ceramic, and polymer AM powder feedstocks. 1.2 This guide provides a description of test methods commonly used to measure moisture and references to their associated standards. 1.3 This guide provides best practice guidance on how to apply the test methods to make them suitable for AM powder characterization. 1.4 This guide is suitable for measuring moisture in AM powder feedstock over the range of 10 µg/g to 10 000 µg/g. 1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.