Near-net-shape Fabrication of Ni(x)Al(y) – TiC Cermets by Binder Jet Additive Manufacturing and Pressure-less Melt Infiltration

Binder jet additive manufacturing effectively replaces preform preparation by traditional powder metallurgy methods and allows more complex geometries to be potentially fabricated. The use of a pressure-less melt infiltration technique provides a method of achieving a fully dense composite in a near-net-shape fashion, cost effective and scalable. TiC preforms (15 x 15 x 10/7.5 mm) were fabricated via Binder Jet Additive Manufacturing and then infiltrated by NiAl₃ and Ni₃Al using a pressure-less melt infiltration technique. Two compositions, Ni₃Al and NiAl₃, were used as infiltrant materials in order to compare wetting behavior and infiltration kinetics.A stark difference in shape retention between Ni₃Al and NiAl₃ infiltrated preforms was observed after infiltration. It was found that the TiC particles in the as printed preform were arranged in an interconnected network structure as a result of the binder jet process and/or sintering step and is responsible for maintaining structural integrity of the printed preform. TiC dissolution by liquid Ni₃Al was significant enough to disband this network structure and force particle rearrangement and lead to poor shape retention. Conversely, TiC particle rearrangement did not occur during infiltration of the Al-rich NiAl₃ alloy and thus the network structure remained intact leading to excellent shape retention of the infiltrated preform.It was found NiAl₃ exhibits a complex melting and solidification behavior where an Al-rich phase segregates heavily from the melted material. The presence of an Alrich inter-particle matrix phase indicates the possibility of a “metered” infiltration process where multiple liquid phases of variant compositions infiltrate the “macro” and “micro” capillaries of the TiC preform in a staggered fashion. The composition and time of infiltration remains unknown and a topic of future work. Additionally, Thermodynamic simulation predicts a reaction at the TiC interface by liquid NiAl₃ to form Al₄C₃, with an interfacial reaction product potentially explaining the lack of TiC dissolution and volumetric shrinkage during and after infiltration by NiAl₃.