D. Welling

Developments in Wire-EDM for the Manufacturing of Fir Tree Slots in Turbine Discs Made of Inconel 718

This paper deals with developments of Wire-EDM technologies for fir tree slot production. The aim of these developments is to substitute certain conventional processes within turbine manufacturing that have been identified as non-optimal like the critical broaching process. Thereby the negative characteristics like inflexible manufacturing processes, high machine tool investment costs and huge energy consumption can be abolished. The objective targets of the conducted research are to meet all safety requirements of the critical components and get an economic manufacturing process. In the first step a special brass wire technology for cutting Ni-based super alloys was developed. Main focus was to meet the requirements of fir tree production concerning aspects of surface integrity and geometry. To measure these aspects on the one hand non-destructive analyses have been performed to guarantee surface roughness and accuracy. On the other hand destructive analyses in terms of cross section polishing for showing thermal influenced rim zones have been prepared. A capable Wire-EDM process is presented.

Multi-scale directed surface topography machined by electro discharge machining in combination with plasma electrolytic conversion for improved osseointegration

Major deficits concerning biodegradable and non-biodegradable orthopaedic implants are a result of insufficient osseointegration and an accelerated corrosion rate. These in turn are significantly influenced by the surface tissue-interface. Cells belonging to different steps of the osteoblast differentiation cascade respond differently to the same surface structure. Therefore, a combination of particular micro and macro structures resulting in a multi-scale directed surface topography may significantly improve the cell response throughout the whole osseointegration process. This paper proposes the possibility to adapt the structural properties of a surface independently throughout different magnitudes of topography by a combination of electro discharge machining and a plasma electrolytic conversion process. Examples of such structures are demonstrated in samples made of the magnesium alloy WE43 as well as the most commonly used titanium alloy for orthopaedic implants Ti6Al4V.