Synchrotron Investigations of cracks in parts produced by laser powder bed fusion additive manufacturing
|SWERIM AB - Material- och Processutveckling
|Funding from Vinnova
|SEK 498 000
|February 2020 - December 2021
|Research infrastructure - utilisation and collaboration
|Industrial pilot projects for the utilisation of neutron and photon based techniques at large-scale infrastructures - Autumn 2019
|2019-05287_Kanthal.pdf (pdf, 167 kB)
Purpose and goal
Porosity is a critical issue in additive manufacturing (AM) of metals. The density of printed parts can be varied by adjusting the process parameters. However, in certain alloy systems, as the ferritic Fe-Cr-Al steels of Kanthal, higher density increases cracking. For Kanthal to be able to produce high quality components, it is therefore important to understand why and when in the process chain these cracks form in order to produce high quality parts. By using synchrotron based XRD and SRµCT it was possible to better understand the link between porosity, residual strain and strain relaxation due to cracking.
Expected results and effects
Clear increase and stronger variation in strain was seen as the porosity decreased while samples still attached to the build plate had a different strain profile. After stress relieving, a low and uniform strain profile was found. Together with the SRµCT-data it is possible to better understand the link between porosity, residual strain and strain relaxations due to cracking. Rapid implementation of this technology in industry for similar investigations is possible through the methodology developed in the project.
Planned approach and implementation
The experiments were performed at the Swedish Materials Science (SMS) beamline P21 by beamline scientist Ulrich Lienert at the Petra III synchrotron in Hamburg, which offers the combination of XRD and SRCT. In order to investigate the effect of porosity levels on crack initiation and propagation in AM parts, 3x4x10mm samples with various porosity levels was analysed (as-built samples with different densities from 97.7% to >99.9%) as well as stress relived samples and samples still attached to the build plate. The six samples required 8 hours of beamtime for the XRD analysis.