A crucial step in the powder bed metal additive manufacturing process is the formation of a thin layer of powder on top of the existing material. The propensity of the powder to form thin layers under the conditions used in additive manufacturing is critically important, but no test method has yet been established to measure this characteristic, which is sometimes referred to as spreadability. The current work spreads a single layer of powder using commercial equipment from the paint and food industries and derives the density of a layer of powder, which is of a similar thickness to that in additive manufacturing. Twenty-four powders from eight suppliers have been tested and the density of the layers has been measured as a function of various parameters. Twenty-two of the powders successfully form thin layers, with a density of at least 40% of each powder’s apparent density. Hall flow time did not correlate with the spread layer density, although the two powders that did not spread did not pass through the Hall funnel. The roughness of the plate onto which the powder was spread, the recoater speed, the layer thickness, particle size and aspect ratio all affect the measured layer density. Results of the new test are repeatable and reproducible. These findings can be used to develop a test for spreadability for metal powders that can be used for additive manufacturing, which will help to improve the quality of printed components. 

The behaviour of metal powders when they are spread into thin layers is critical for powder bed additive manufacturing and other processes. However, there is no accepted test procedure to quantify this behaviour. There is not even an accepted metric that can be used to assess this property. This increases the difficulty of developing new powders for additive manufacturing. The current study proposes test and analysis procedures that minimise the influence of operators and are aimed at providing maximum repeatability and reproducibility while minimising the need for specialist analysis equipment. Initial testing shows that a powder with good flow properties behaves as expected as a function of recoater speeds and always exhibits superior spread metrics to powders with poor flow properties. This provides an important step towards the establishment of a robust, inexpensive test that can help additive manufacturing to grow in new industries. 

The spreading of powders into thin layers is a critical step in powder bed additive manufacturing, but there is no accepted technique to test it. There is not even a metric that can be used to describe spreading behaviour. A robust, image-based measurement procedure has been developed and can be implemented at modest cost and with minimal training. The analysis is automated to derive quantitative information about the characteristics of the spread layer. The technique has been demonstrated for three powders to quantify their spreading behaviour as a function of layer thickness and spreading speed.