Due to increasing material requirements of high temperature aerospace applications current state-of-the-art Ni-based superalloys need to be further developed or replaced. B2-NiAl exhibits a low density of only two thirds of comparable Ni-based super alloys. Moreover, the high melting temperature of 1638 °C, a superior thermal conductivity and an outstanding oxidation resistance at elevated temperatures of B2-NiAl make NiAl-based alloys a promising material for high temperature applications in future turbine engines. However, the unsolved issues of a limited ductility and fracture toughness at room temperature as well as a poor strength at high temperatures have prevented industrial utilization so far. The Additive Manufacturing (AM) technique Laser Metal Deposition (LMD) combines the advantages of near net shape manufacturing, tailored thermal process conditions and in-situ alloy modification. Due to the functional principle of LMD the composition of the powder blend, being fed into the process zone can be modified in-situ. Hence, alloying and material build up can be achieved simultaneously. These process characteristics might be the key for overcoming the challenges in processing NiAl-based alloys.
Within this contribution the AM processing of B2-NiAl by means of LMD shall be presented. The manufacturing approaches LMD of elemental powder blends as well as LMD of pre-alloyed powders were investigated in detail. Firstly, for both approaches a feasibility study was conducted with respect to the fabrication of representative test geometries. Secondly, by variation of the parameters laser power, feeding rate and pre-heating temperature process-microstructure relationships were analyzed by optical microscopy (OM), scanning electron microscopy (SEM) as well as x-ray diffraction (XRD) analysis. Based on the obtained data the manufacturing approaches were compared comprehensively in order to achieve an in-depth understanding of AM processing of NiAl-based alloys as well as in-situ alloy formation during LMD.