Microstructure and mechanical properties of WB₂–B₄C composites fabricated by boro/carbothermal reduction and SPS

Abstract

The phase composition, microstructure, and mechanical properties of the WB2–B4C composites fabricated by a combination of boro/carbothermal reduction and spark plasma sintering (SPS) method with WO3, B4C, and graphite as raw materials were investigated in this study. The experimental results showed that the relative density of the as‐sintered WB2–B4C composites was ∼93.1% and ∼99.5%, respectively, after being SPS sintered at 1600°C under the applied load of 30 MPa for 10 min. Scanning electron microscope analysis showed that a network structure with WB2 grains surrounded by B4C grains was observed after sintering. Analyses of high‐resolution TEM showed semi‐coherent interface and lattice distortion transition region between WB2 and B4C grains. The Vickers hardness of WB2–B4C composite increased to 22.3 ± 0.9 GPa at 9.8 N owing to the fully dense, solid solution of C, and three‐dimensional network structure. Moreover, the fracture toughness and flexural strength of WB2–B4C composite reach 6.04 ± 0.81 MPa m1/2 and 750 ± 80 MPa, respectively, which could be attributed to the semi‐coherent interface between WB2 and B4C grains.

Thermal stability of ReB2‐type transition metal diborides

“…Factor group analysis of all the samples results in two E 1g and two E 2g Raman active phonon modes, where E 1g and E 2g modes are reported as B-B pair atom vibrations in a-b plane of the unit cell as "out-of-phase" vibrations with a calculated phonon energy of 85.2 MeV for E 1g mode and 90. 4 MeV for E 2g mode 4. 29 It could be predicted from partial density-ofstate that the vibration amplitude of ReB 2 -type borides in the low frequency range (<300 cm −1 ) would be very small, which could be mainly attributed to the motion of transition metal(s).…”

“…[1][2][3] Among them, transition metal borides (TMBs), which can be synthesized at ambient pressure and therefore generally reduce the production costs, have attracted much attention. [4][5][6][7] In recent years, efforts have been made on transition metal diboride (TMB 2 ) (TM = Re, Os, Ru, W, etc.) materials, which have been proven to have high hardness both theoretically and experimentally.…”

“…Compounds consisting of transition metals (TMs) and light elements such as B, C, and N have been identified as potential new type of superhard materials due to their excellent physical properties, such as electrical conductivity, high incompressibility, high shear strength, and exceptionally high hardness 1–3 . Among them, transition metal borides (TMBs), which can be synthesized at ambient pressure and therefore generally reduce the production costs, have attracted much attention 4–7 . In recent years, efforts have been made on transition metal diboride (TMB 2 ) (TM = Re, Os, Ru, W, etc.)…”

In‐situ reaction sintered ReB2–B4C composite by reactive spark plasma sintering

“…In our previous work, the Vickers hardness of the WB 2 –B 4 C composite prepared by a combination of boro/carbothermal reduction and SPS techniques was found to be increased by 23 % compared with the monolithic WB 2 . In addition, the fracture toughness of sintered sample reached 6.04 ± 0.81 MPa·m 1/2 because of good bonding between grains 18 …”

“…In addition, the fracture toughness of sintered sample reached 6.04 ± 0.81 MPa⋅m 1/2 because of good bonding between grains. 18 In the present work, ReB 2 -B 4 C composite was fabricated via reactive spark plasma sintering assisted by high energy ball milling from raw materials of Re and B 13 C 2 . The phase composition, microstructure, Vickers hardness, and the fracture toughness of the obtained composites were characterized; the reaction thermodynamics were analyzed, and the reaction mechanism was clarified.…”