In December 2018, spin and burst tests of four additively manufactured turbo pump impellers were carried out successfully. Turbopump impellers are highly loaded and highly demanding components used in liquid fuel rocket engines. They are key components to feed the combustion chamber of the rocket engine with the propellants at high pressure and high mass flow.
Within the DLR-project “SeLEC – Selective Laser Melting of Rocket Engine Components”, a full manufacturing chain for shrouded impellers was developed in the department Metallic Structures and Hybrid Materials Systems, which covers the additive manufacturing at the DLR Institute of Materials Research. The impellers were designed at the DLR Institute of Space Propulsion. The manufacturing chain for selective laser melting (SLM) from a Ti-6-Al-4-V alloy included various aspects from powder and materials characterization, SLM process development, build strategy to post-processing. The impeller was designed as technology demonstrator for an upper stage liquid rocket propulsion engine.
Three spin tests were carried out with expansion measurements at 62.000 rpm (slightly above service speeds), validating the developed manufacturing route. In a final burst test, neither failure nor deformation of the component was observed despite reaching rotational speeds above 166.000 rpm. The material resisted the enormous centrifugal forces, which resulted only in elastic deformations during the high speed tests.