Bulk Cr7C3 compound fabricated by mechanical ball milling and plasma activated sintering

•As milling time changes from 1 h to 15 h, new phase will not appear.•At sintering temperature of 1648 K, Cr23C6 compound forms besides Cr7C3.•As sintering temperature reaches 1673 K, the bulk Cr7C3 can be fabricated.•At the sintering temperature of 1698 K, the cracks appear on the bulk Cr7C3.•With increasing sintering time, the strength and toughness increase firstly and then decrease.

Bulk Cr7C3 compounds were fabricated with Cr and C mixed-powder by mechanical ball milling and plasma activated sintering (PAS). The results indicate that, there is no alloying reaction between Cr and C powders at milling times from 3 h to 15 h; at milling times from 1 h to 7 h, the morphology of mixed-powder becomes finer and the distribution becomes more and more uniform; however, as milling time exceeds 7 h, the morphology and distribution have no obvious change. At sintering temperature of 1648 K for 2 h duration, there is also Cr23C6 compound besides Cr7C3. With sintering temperature reaching 1673 K and above, the single bulk Cr7C3 compound can be fabricated; however, the cracks appear at 1698 K. The result also indicates that, as sintering time increases from 2 h to 4 h at 1673 K, the relative density of bulk Cr7C3 will increase; however, as the sintering time exceeds 4 h, the density has no obvious change. Furthermore, the hardness of bulk Cr7C3 increases slightly with sintering time. The bending strength and fracture toughness increase with the sintering time changing from 2 h to 4 h; however, they decrease slightly with the time exceeding 4 h.