A Comparison of the Spreadability and Flowability of Metal Powders for AM Applications
The ability of a powder to form a consistent layer in an additive manufacturing (AM) machine plays a critical role in producing high-quality parts. This property is known as powder spreadability.
Several definitions of powder spreadability exist. However, the industry has not yet reached a consensus on how to measure it. AM machines often use in-situ techniques to analyse powder layer formation. These methods mainly support process monitoring rather than predictive powder testing.
Researchers have proposed several tests and devices to assess powder spreadability.¹⁻⁴ These include automated test beds that spread powder across a test surface. Manual spreading devices can also replicate aspects of the powder deposition process.
Most spreadability tests use optical analysis to examine the resulting powder layer. This approach can reveal variations in surface coverage and layer uniformity. Some methods also measure the density of the powder layer. They do this by weighing the powder and calculating the volume of the spread layer.
However, spreadability does not depend on a single powder characteristic. Particle size, particle shape, density and surface properties can all influence how a powder behaves during spreading. Flowability also plays an important role. A powder must move consistently as the recoater or spreading mechanism distributes it across the build platform.
Good flowability does not always guarantee good spreadability. A powder may flow well under one set of conditions but behave differently during the spreading process. Factors such as powder packing, cohesion and particle interactions can affect the final layer.
For this reason, comparing powder flowability with spreadability can provide valuable insight into AM powder performance. Flowability tests can help identify differences between powders before they enter the manufacturing process. Direct spreadability tests can then show how those differences affect layer formation.
This application note compares the spreadability and flowability of metal powders used in AM applications. The results demonstrate how these two properties relate and highlight the value of characterising powder behaviour before production.
