Scientists from the German Federal Institute for Materials Research and Testing (BAM) have made use of neutrons to non-destructively test 3D printed gas turbine components.
Air-cooled latticed turbine buckets operate at extreme temperatures and pressures within gas turbines. Their complex structure can be created additively, with selective laser sintering.
The only drawback here is that highly localized heat and the rapid cooling associated with laser sintering can lead to residual stress in components produced this way.
Manufacturers generally address this issue with a downstream heat treatment process, but this additional step costs time and money.
As part of BAM’s research, Siemens Energy printed a lattice structure just a few millimeters in size using a nickel-chrome alloy typically used for gas turbine components.
The usual heat-treatment after production was intentionally omitted.
“We wanted to see whether or not we could use neutrons to detect internal stresses in this complex component,” says lead scientist Dr Tobias Fritsch.
“We’re very glad to be able to make measurements in the Heinz Maier-Leibnitz Zentrum in Garching; with the equipment provided by STRESS-SPEC we were even able to resolve internal stress in lattice structures as intricate and complex as these.”
The next step for Fritsch and his team will be to consistently reduce this destructive stress by adjusting the manufacturing process.
“We know that we have to modify the production process parameters and thus the way in which the component is built up during printing,” notes Fritsch.
“The more localized the heat application is during the melting process, the more internal stress results.”
Image and content: Dr. Tobias Fritsch-BAM via The Engineer