An Assessment of Bulk and Surface Residual Stress in Selective Laser Melted Inconel 718

Speaker:
Thiede, Tobias; BAM Bundesanstalt fur Materialforschung und -prufung; Germany

Authors:
Thiede, T.; Federal Institute for Materials Research and Testing (BAM); Germany
Cabeza, S.; Institut Laue-Langevin; France
Mishurova, T.; Federal Institute for Materials Research and Testing (BAM); Germany
Nadammal, N.; Federal Institute for Materials Research and Testing (BAM); Germany
Kromm, A.; Federal Institute for Materials Research and Testing (BAM); Germany
Bode, J.; Federal Institute for Materials Research and Testing (BAM); Germany
Haberland, C.; Siemens AG; Germany
Bruno, G.; Federal Institute for Materials Research and Testing (BAM); Germany

ID: ECNDT-0315-2018
Download: PDF
Session: Additive Manufacturing – characterisation
Room: H1
Date: 2018-06-11
Time: 15:20 - 15:40

Having been introduced almost two decades ago, Additive Manufacturing (AM) of metals has become industrially viable for a large variety of applications, including aerospace, automotive and medicine. Powder bed techniques such as Selective Laser Melting (SLM) based on layer-by-layer deposition and laser melt enable numerous degrees of freedom for the geometrical design. Developing during the manufacturing process, residual stresses may limit the application of SLM parts by reducing the load bearing capacity as well as induce unwanted distortion depending on the boundary conditions specified in manufacturing.
The residual stress distribution in IN718 elongated prisms produced by SLM was studied non-destructively by means of neutron (bulk) and laboratory X-ray (surface) diffraction. The samples with different scanning strategies, i.e. hatching length, were measured in as-build condition (on a build plate) and after removal from the build plate.
The absolute values of all stress components decreased after removal from the build plate. Together with surface scan utilizing a coordinate-measuring machine (CMM), it is possible to link the stress release to the sample distortion. Obtained results indicated different residual stress states for each of the transversal, longitudinal and normal component depending on the thermal gradient in the respective direction.