Microstructure and hardness comparison of as-built inconel 625 alloy following various additive manufacturing processes

Experimental examples of as-built microstructures and associated microindentation hardnesses (HV) for a wide range of metal additive manufacturing (AM) processes for Inconel 625 alloy are presented in this research paper. These processes included cold spray, laser powder bed fusion, wire arc additive manufacturing, electron beam directed energy deposition, laser hot wire, binder jetting, laser power directed energy deposition, electron beam melting, and laser wire directed energy deposition. Microstructures ranged from impact bonded, flattened 625 alloy grains containing microdendrites and dislocations, having a microindentation hardness of HV 590 for cold spray, to large, equiaxed grains for binder jet-printed components having a microindentation hardness of HV 180. Electron and laser beam melt-related processes, including wire and powder feeds, produced varying sizes of columnar grains with parallel and cellular arrays of microdendrites, having microindentation hardnesses ranging from HV 304 to HV 228. Delta phase precipitate needles were also produced in laser-powered directed energy deposition microstructures along with columns of gamma double-prime precipitates for electron beam melting. The results demonstrate a range of AM processes applications and strategies to produce as-built and surface-modified Inconel 625 alloy products and components. These results demonstrate differences in the microstructure from the various AM processes and considerations for use in end use applications.