Analysing the texture of superalloys produced by additive manufacturing

Neutron diffraction reveals how the microstructure of nickel superalloy specimens are affected by the additive manufacturing parameters.

The challenge

Additive manufacturing is a technique that can be used to build metal components layer by layer, to the specification of a 3D model. This enables intricate parts to be made at a small scale without the need to invest in niche manufacturing equipment. However, alloys produced by additive manufacturing can develop a strong texture that affects their mechanical properties, and hence a component’s performance.

A Canadian research collaboration, including Siemens Energy, wanted to understand the microstructural changes caused by altering various parameters during laser powder bed fusion (LPBF) additive manufacturing. They focussed on components made from a nickel-based superalloy known as Hastelloy‑X, which is used to make gas turbines.

The experiment

The researchers used the specialised setup on the ENGIN-X beamline at ISIS Neutron and Muon Source to test how Hastelloy‑X components behave under operational conditions, using neutron diffraction to characterise residual stresses and texturing under compression.

The results

The team determined that the specific energy, power and scanning speed of the laser influence the microstructure of Hastelloy‑X samples, with increasing laser power inducing a preferred orientation of the grains.
This initial study confirms that it is crucial to control the individual parameters of LPBF, as this will determine the structure, and therefore properties, of the end component.

“The laser powder-bed fusion additive manufacturing process produces an intense temperature gradient within the fabricated components as a result of the fast thermal and cooling cycles that occur during the process. Therefore, residual stresses and deformations are inevitable in the manufactured parts. In order to minimise deformation, residual stresses must be measured and analysed to optimise the LPBF process parameters. Due to the capabilities available at ENGIN-X, we were able to measure residual stresses precisely.”

Ali Bonakdar
Advanced Manufacturing Research Lead, Siemens Energy