Electrolytic processing of NiTi shape memory alloys

The manufacturing of high-grade products made of nickel–titanium shape-memory alloys (NiTi-SMA) causes high demands on the surface finishing. The disadvantage of mechanical procedures is the emerging of deformation layers, whereas thermal treatment may lead to a modification of the function properties of the NiTi-SMA in the heat-affected surface zone. With electrolytic procedures it is possible to remove these zones even on smallest, finely structured components and to debur them due to the increased material degradation on the edges. Therefore, this finishing process is of great importance not only for micro-system technology but also for components with elaborately manufactured structures. A further field of application is the surface preparation for coating. s work NiTi-SMA of different initial topologies were electro-polished in austenitic and martensitic state and the development of roughness was recorded depending on time. Satisfactory results from all initial surfaces were to be achieved. However, longer polishing periods lead to the formation of waves due to material segregation. rmore, the paper shows that the corrosive properties of a NiTi-SMA are not only dependent on the surface treatment but also on the initial topology of the surface.