Method for manufacturing a metallic component by additive laser manufacturing

A method for manufacturing a three-dimensional metallic article/component made of a Ni-, Co-, Fe-based superalloy or combinations thereof, entirely or partly, having a microstructure with adjusted grain sizes to the load conditions of said article/component, by an additive manufacturing process selected from the group of selective laser melting (SLM)or selective laser sintering (SLS), using a metallic base material in powder form, wherein said adjusted grain sizes are directly generated during said additive manufacturing process, said method comprising:

• a) generating a three-dimensional model of said article followed by a slicing process to calculate the cross sections;
• b) passing said calculated cross sections to a machine control unit afterwards;
• c) providing a powder of said base material, which is needed for the process;
• d) preparing a powder layer with a regular and uniform thickness on a substrate plate or on a previously processed powder layer or on a conventionally manufactured preform;
• e) performing powder melting by scanning with an energy beam in an area corresponding to a cross section of said article according to the three-dimensional model stored in the control unit ;
• f) lowering the upper surface of the previously formed cross section by one layer thickness;
• g) repeating said steps from c) to f) until reaching the last cross section according to the three-dimensional model and
• h) optionally heat treating said three-dimensional article,
• wherein in step e) a dual laser setup is used, where two laser beams of different beam properties are combined in the same machine and by adjusted beam profiling and integration of a suitable beam switch in a controlled manner a switching between two different laser beam diameters is performed, and wherein in each layer the laser beam with the smaller diameter scans the whole area thereby creating fine grain sizes and in every kth layer, with k>1, the laser beam with the larger diameter scans the area where a coarse grain size is needed thereby remelting the area with fine grain sizes.