Processing of novel ZrB2-Inconel 718 cermets by freeze casting and pressureless spark plasma sintering

The fabrication of novel ZrB2-Inconel 718 cermets, containing 10-50 vol% of the latter, through an innovative route combining freeze casting and pressureless spark plasma sintering was investigated. It is shown that fully dense cermets were fabricated, having twice the hardness of the Inconel 718 superalloy and thrice the toughness of the ZrB2 ceramic they were made of. Microstructural characterisation using scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffractometry revealed the partial dissolution of ZrB2 grains into the metallic binder during sintering, which triggered the precipitation of a Ni-Zr intermetallic, Zr oxides, and Cr boride instead of the typical metal carbides appearing in the pure superalloy subjected to the same sintering cycle. The proposed innovative processing approach is promising for producing high-performance cermets with tailored mechanical properties for use in demanding sectors like aerospace, aviation, or energy generation and storage.