Phase Formation and Physical and Mechanical Properties of Fe‒Cu–Ni‒Sn–VN Composites Sintered by Vacuum Hot Pressing for the Diamond Stone Processing Tools

The effect of the concentration of vanadium nitride additive (in the range from 0 to 10 wt %) on the phase formation, hardness, and fracture toughness of composite diamond-containing materials based on the 51Fe–32Cu–9Ni–8Sn matrix molded by cold pressing and subsequent vacuum hot pressing is investigated. It is found that the addition of 10 wt % of vanadium nitride to the 51Fe–32Cu–9Ni–8Sn composite is accompanied by an increase in the hardness from 3.86 to 8.58 GPa with a slight decrease in the fracture toughness from 5.55 to 4.76 MPa m1/2. Moreover, the H(CVN) dependence has two characteristic segments that differ in the slope. The hardness increases insignificantly (from 3.86 to 5.26 GPa) in the range of 0 < CVN < 4 wt %, while the second region (CVN > 4 wt %) is characterized by a more substantial increase in the hardness and a more significant decrease in the grain size. It is shown that these parameters are achieved owing to the dispersion mechanism of strengthening and modification of the structure (a decrease in the mean particle size of the matrix phase, the formation of new (Fe3Ni)0.5 and Cu3Fe17 phases, and the precipitation of primary and secondary phases of vanadium nitride) and phase composition of the composites.