Researchers at the Fraunhofer Institute for Laser Technology ILT, working as part of the EU-sponsored Fantasia project, have demonstrated that complex components for use in aircraft engines can be produced quickly and at a reasonable price using selective laser melting processes.
Aircraft engine components must perform under extreme conditions: they must rotate more than 1000 times per second, and withstand temperatures of up to 2000°C and extreme pressures. At the same time, they should be lightweight and satisfy stringent standards for safety. Given all of these factors, the tasks of developing and servicing aircraft engines pose major challenges for engineers. Researchers at the Fraunhofer Institute for Laser Technology ILT in Aachen, Germany, have been investigating the suitability of selective laser melting (SLM). With this method, the part can be built up, layer by layer, on a building platform using a powder-based material. In essence, this process is comparable to that of a computer printer, except that it takes place in three dimensions. Based on computer-generated design data for the planned part, the metal powder is applied to the appropriate areas of the substrate and then immediately melted into place with a high-power laser beam. This forms a permanent bond with the portion of the object that is already complete – and materials tests have found that the quality of components produced using this method is at least as high as that of parts manufactured using conventional methods.
'With this process we can not only make perfect repairs to damaged engine parts but also build complete components that cannot be produced using conventional methods such as milling or casting,' observed Dr Konrad Wissenbach of ILT. 'This also permits the kinds of geometries and designs we once could only dream of.' With using laser-based generative methods, manufacturing cycle times can be reduced by 40 per cent or more relative to conventional techniques. In the future, this could mean savings of up to 50 per cent of the material required, and at least 40 per cent of repair costs. Wissenbach was coordinator of the €6.5m, EU-sponsored Fantasia project – an acronym standing for 'fexible and near-net-shaped generative manufacturing chains and repair techniques for complex shaped aero engine parts,' which ended in May 2010.
The SLM approach is not yet suitable for every turbine material. 'We have already seen very good results with Inconel 718, a nickel-based superalloy, and with titanium alloys as well,' Wissenbach remarked. 'We are not quite as far along with other fissure-prone materials.' ILT researchers are continuing the search for ways of using melting or moulding to reseal any cracks a part may have developed during use. The productivity of the method also needs further improvement, because with a coating thickness of 30-100µm, larger components can take quite a long time to produce.