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.