Due to the increasing complexity of industrial applications components need to fulfill significantly rising requirements in terms of mechanical, thermo-physical as well as geometrical properties. Usually these requirements can not be fulfilled by only one material. Besides various advantages such as the build-up of highly complex structures or the possibility of functional integration, the additive manufacturing (AM) process laser metal deposition (LMD) allows the simultaneous fabrication of multiple materials. This multi-material processing by LMD can strongly increase the range of applications for AM within several industrial branches such as the energy sector, aerospace or medical technology.
The usage of multiple materials within one component enables designers and engineers to use specific materials with specific properties just in the region where they are needed. One example of this application is the use of materials with high thermal conductivity (e.g. copper alloys) in the components areas where an increased heat flux is required. The remaining areas can be fabricated by high strength alloys (e.g. stainless-steel alloys) to maintain required mechanical properties.
The LMD process allows a temporal and local control of the powders being fed into the process zone. Hence, material transition, which can also be observed in nature, such as sharp material intersections (materials with similar thermo-physical properties) as well as functionally graded three-dimensional transition zones (materials with severely different thermo-physical properties), can be applied by LMD. Moreover, the usage of interlayers enables the fabrication of materials with limited metallurgical compatibility by means of LMD.
In this contribution the wide possibilities of multi-material processing by LMD are presented. The work focuses on challenges and solutions for the fabrication of sharp material intersections and functionally graded structures by LMD (e.g. multi-material transition from SS 316L to Inconel 718). The phenomena concerning the formation of intermetallics, in-situ alloying processes as well as intra-layer composition changes are investigated in-depth and mechanisms to understand these phenomena in detail are suggested.