Experimental investigation of the microstructure design in laser powder bed fusion using In625
Additive manufacturing processes, such as laser based powder bed fusion (LPBF), provide new process- and material-specific possibilities, which can be used to generate extra value compared to conventional manufacturing processes. The LPBF process enables local microstructure designs, for example. Usually the main process parameters, such as laser power, scan speed and scan path distance, are kept constant for each part. However, by locally changing these parameters it is possible to generate locally varying properties in components. In this way, graded microstructure properties can also be adjusted, which lead to locally varying mechanical properties. Components with graded microstructural properties have specifically altered material composition, properties or microstructural states with defined transitions between the altered areas.
In this paper, the melt pool geometry is varied via the laser power using a voxel-based approach in order to generate specific local mechanical properties via the microstructure. First, a process window for dense parts (relative density < 99.5 %) is investigated, in order to determine the influence of the laser power on hardness and microstructure at constant scanning speed and constant scan path distance. Subsequently, the effects of property grading on the material properties (here: hardness) and the microstructure of the underlying layers are investigated. Finally, a comparison between graded and non-graded tensile specimens is made to show the advantages of microstructure design.