The effect of carbon on phase composition and microstructure of cermets based on Mo2NiB2 boride

This work investigates the effect of carbon alloying on the phase composition and microstructure of cermets based on the ternary boride Mo2NiB2. The sequence of precipitation of hard phases depending on the Mo/(B + C) ratio was determined. It is shown that at Mo/(B + C) close to 1, the phase composition is represented by boride Mo2NiB2, carbide Mo2C and nickel binder. The increase of Mo/(B + C) ratio leads first to the formation of additional Mo2C carbide, characterized by increased nickel content, and then to the appearance of κ-phase Mo10Ni3C3B. The relationship between the phase formation, porosity, hardness and fracture toughness of sintered cermets is revealed.