In business environments, among a slew of completely new range of possibilities of 3D printing, production of new turbine buckets is one. However, 3D printing is often associated with internal stress in mechanical components, which in the worst case, can lead to cracks.
Following a research initiative, a research team has been successful to use neutrons from the Technical University of Munich. The success to use the source of research neutron for non-destructive detection of internal stress is a key achievement in the improvement of production processes.
In fact, for 3D printing, in mechanical environments, gas turbine buckets have to handle extreme ambient conditions. For example, at high temperatures and under high pressure gas turbine buckets are subject to tremendous centrifugal forces. Thus, to maximize energy yield further, the gas turbine buckets need to hold temperatures which is actually higher than the melting point of the constituent material. To enable this, hollow turbine buckets are used which are air-cooled from inside.
Interestingly, the gas turbine buckets can be made employing laser powder bed fusion – a step by step adding manufacturing technology. To get started, the starter material in powder form is added layer by layer by selectively melting using laser. For example, in avian bones, the intricate lattice constructin inside the hollow turbine pockets provides necessary support to the corresponding part.
“Meanwhile, it would be impossible to create components with such intricate structures using conventional methods such as milling or casting,” stated ax expert at the German Federal Institute of Materials Research and Testing.
Nonetheless, the highly localized heat input of the laser and rapid cooling of the melt pool in 3D printing lead to residual stress in the material.