Physical and Mechanical Properties of Composite Diamond-Containing Materials Based on Fe-Cu-Ni-Sn-VN Matrices Sintered by Vacuum Hot Pressing

The effects of the concentration of the nano-VN additive (in the range from 0 to 10 wt %) on the structure, the retention of diamond grains by metal matrix, and the mechanical properties (nanohardness H, elastic modulus E, stability of the material to elastic deformation H/E, and resistance of the material to plastic deformation H-3/E-2) of samples of composite diamond-containing materials (CDMs) based on the 51Fe-32Cu-9Ni-8Sn matrix formed by cold pressing with subsequent vacuum hot pressing are studied. It is shown that the structure of the sintered CDM sample based on the 51Fe-32Cu-9Ni-8Sn matrix consists of diamond grains and fcc solid solutions that contain iron, copper, nickel, and tin in different ratios. Under this condition, elements Fe, Cu, Ni, and Sn are not detected on the surface of diamond grains, and gaps and discontinuity flaws are observed at the diamond-matrix contact. The additions of nano-VN added to the composition of the CDM in the amounts of 2, 4, 6, and 8 wt % allow one to obtain more finely grained structures composed of solid solutions containing iron, copper, nickel, vanadium, and tin, as well as diamond grains, on the surfaces of which small amounts of the same elements are present. At the same time, the diamond-containing matrix contact is tight without visible gaps, discontinuity flaws, and other defects. It is found that the variation of the concentration of vanadium nitride is accompanied by a nonmonotonic change in H for the entire studied interval of the depth of indenter immersion into the sintered sample surfaces. The addition of 2 wt % nano-VN to the DCM provides increases in the H value of the matrix from 5.2 to 5.6 GPa, in the E value from 197 to 202 GPa, in the H/E ratio from 0.0264 to 0.0277, and in the H-3/E-2 ratio from 3.62 to 4.30 MPa. The largest increases in H (7.8 GPa), E (213 GPa), H/E (0.036), and H-3/E-2 (10.46 MPa) are found for the CDM sample containing nano-VN additive in the amount of 8 wt %. These characteristics are achieved owing to the dispersion mechanism of strengthening and the modification of the structure (a decrease in the mean grain size, the creation of a tight diamond-matrix contact, the formation of V, Fe, Ni, and Cu inclusions on the surface of diamond grains, and the disappearance of pores in the metal matrix) and phase composition of the composites.