MAPP – In situ ball indentation process to assess powder flowability

This study used X-ray micro-computed tomography (XMCT) to reveal the ball indentation process in 3D and develop a further understanding of the powder packing behaviour during the process. The XMCT also allows us to quantify the packing density of powders at different regions of the powderbed during ball indentation at different penetration depths and track the powder movement.

Flow resistance and flowability are important properties of powders for additive manufacturing,which havegreat influences on the mechanical properties of the end products. The ball indentation technique provides a measure of hardness which can be related to flow resistance and flowability on powders. However, it is challenging to attain a reliable indentation process. In-situ micro-X-raytomography is known as a non-destructive method that can reveal the movement of powders during the indentation process. It also allows us to quantify the different layer packing fractions and localise consolidation.

The experiment was carried out at the National X-ray Computed Tomography lab, University ofManchester.As shown in Figure 1, CT 5000 rig (Deben, UK) was installed on top of the rotationstage of Versa 620 CT scanner (Zeiss, Germany). Ti alloy powders thatwere manufactured via gasatomization were sieved and loosely filled into a 10-mm diameter container. It was then mountedon the bottom grip of the rig, while a glass ball indenter was fixed on the top grip of the rig. Therefore,it allows us to precisely control different penetration depths (from 10% to 40% of the ball diameters)of the indentation. A series of projections were acquired while the rig was rotating within the CTscanner.