Physicomechanical Properties of the Matrix Material of Сdiamond–(Fe–Cr–Cu–Ni–Sn) Composite Materials Formed by Spark Plasma Sintering

Abstract

For the (26Fe–25Cr–32Cu–9Ni–8Sn) + ZrO₂ matrix material used in С_diamond–(Fe–Cr–Cu–Ni–Sn) composite materials formed by spark plasma sintering, the dependences of the relative density ρ_rel, ultimate compression R_cm and bending R_bm strength, microhardness H_V, and fracture toughness K_Iс on the zirconia content has been established by using samples with different ZrO₂ content. The addition of 10% ZrO₂ to the 26Fe–25Cr–32Cu–9Ni–8Sn composite increases the relative density ρ_rel from 0.987 to 0.997, the ultimate compression strength R_cm from 950 ± 35 to 1510 ± 45 MPa, the ultimate bending strength R_bm from 750 ± 20 to 1140 ± 35 MPa, the microhardness H_V from 8.0 ± 0.25 to 9.0 ± 0.42 GPa, and the fracture toughness K_Iс from 6.5 ± 0.35 to 9.2 ± 0.42 MPa m^0.5. Such parameters are caused by tetragonal t-ZrO₂ phase transformation and, correspondingly, an increasing role of transformation strengthening, and a decrease in the grain size, as ZrO₂ is an inhibitor of grains for the major Fe and Cr phases under sintering. In the 26Fe–25Cr–32Cu–9Ni–8Sn sample (\({{C}_{{{\text{Zr}}{{{\text{O}}}_{{\text{2}}}}}}}\) = 0%) under indentation, there occur many cracks of considerable size both in the inner area of a Vickers pyramid imprint and around it to result in excessive brittleness and destruction in the material. This is due to agglomeration in the process of mixing the components, their separation under sintering, and the formation of micropores and microcracks to be a main reason of low values for ρ_rel, R_cm, R_bm, H_V, and K_Iс. At a zirconia nanopowder content \({{C}_{{{\text{Zr}}{{{\text{O}}}_{{\text{2}}}}}}}\) = 10%, the cracks in the matrix near the indentor imprint become poorly visible, and the material is not almost destructed in the vicinity of the indentor imprint. The results obtained for the relative density ρ_rel in combination with high mechanical characteristics (R_cm, R_bm, H_V, and K_Iс) of sintered (26Fe–25Cr–32Cu–9Ni–8Sn) + ZrO₂ matrix material samples enable their application for the production of composite diamond-containing materials with increased mechanical and service characteristics.