Steel parts with tailored material gradients by 3D-printing using nano-particulate ink

It is difficult to generate any user-defined three dimensional gradient to tailor the functional properties of a component. Problems are not only the lack of local material design tools, but also a suitable manufacturing process. The implementation of the concept of local composition control into the Solid Freeform Fabrication (SFF) process 3D-Printing is described, which leads to geometrical complex parts out of tailored materials. Suspensions of different functional inks containing a binder and carbon black nano-particles are dispensed into droplets through multiple jets - like inkjet printing a halftone image on a paper - but into a metal powder bed to generate layer by layer graded green parts. In this case the tailored preforms are then sintered, while the nano-particle additions from the functional ink act locally as alloying elements in the steel matrix to combine e.g. both, toughness and hardness in the part. This work concentrates on the realisation of the new process and shows first results taking the generation of carbon-graded steel parts as an example.