A team of scientists from the Australian Nuclear Science & Technology Organisation (ANSTO) as well as from overseas have discovered how to theoretically avoid cracks and deformations in metal parts created with 3D printers, with potential benefits for the aviation industry.

The team, led by the Linköping University in Sweden, travelled to ANSTO’s Lucas Heights Campus prior to commencement of the COVID-19 pandemic to study how the orientation of the part impacts the additive manufacturing (AM) process. Using ANSTO’s Kowari strain scanner, a scientific, non-destructive technique known as neutron diffraction was used to measure and characterise residual stresses within nickel-based superalloy samples that were produced by selective laser melting (SLM) AM method. Superalloys are an important group of high-temperature metals and are often used in the hottest sections of jet and rocket engines, where temperatures can reach 1,200 to 1400 degrees Celsius.

The technique, which allows you to “see inside” a material without damaging it, is used at ANSTO to study materials commonly used in industry. It can reveal information about the structural integrity of pipes, rail and bridge sections, along with many other metal components.

The research concluded that the particular direction in which metal parts are physically oriented, will significantly impact the formation of residual stresses, and therefore has the potential to prevent unwanted deformation or cracks in the AM part. When investigating various orientations of printed samples, the team found that for ‘L-shaped’ parts, the horizontal position resulted in the least residual stress.

The new findings represent a step forward in controlling the properties of AM parts and could eventually mean savings and more durable engine parts for the aviation industry. Measurements on the Kowari strain scanner provided a better understanding of how the orientation of specific parts contributes to the development of residual stresses during the AM process. This research reveals that in AM, it is very important to look at the orientation of the part – in order to find out which direction is best to build up that particular part during manufacture.

When manufacturers are making parts, they cannot see what stresses are building up inside the materials, but this approach enables them to predict stresses beforehand, Neutron scattering confirmed that the predictive models were correct. More work is planned to investigate how different scanning strategies and laser power influence the development of residual stresses.