Zirconium Carbide–Tungsten Cermets Prepared by In Situ Reaction Sintering

Abstract

Zirconium carbide–tungsten (ZrC–W) cermets were prepared by a novel in situ reaction sintering process. Compacted stoichiometric zirconium oxide (ZrO2) and tungsten carbide (WC) powders were heated to 2100°C, which produced cermets with 35 vol% ZrC and 65 vol% W consisting of an interpenetrating‐type microstructure with a relative density of ∼95%. The cermets had an elastic modulus of 274 GPa, a fracture toughness of 8.3 MPa·m1/2, and a flexural strength of 402 MPa. The ZrC content could be increased by adding excess ZrC or ZrO2 and carbon to the precursors, which increased the density to >98%. The solid‐state reaction between WC and ZrO2 and W–ZrC solid solution were also studied thermodynamically and experimentally.

Microstructures and properties of ultrafine grained W–ZrC composites

“…Thus, studies of oxides have shown their limitations for high-temperature applications due to the relatively low melting points of the oxides [5]. Therefore, systems containing carbides and nitrides with high melting points have also been investigated [21][22][23].…”

Microstructure and properties of W–ZrC composites prepared by the displacive compensation of porosity (DCP) method

“…Compared with the composites prepared by hot pressing and reactive sintering [9,13], the properties were not very good. One reason was that the content of tungsten was much smaller, the maximum content was 38 vol.% theoretically when all WC powder reacted to form W and ZrC, while the content was at least 60 vol.% in the composites prepared by hot pressing or reactive sintering.…”

“…W-ZrC composites were also produced via in situ reaction sintering by Zhang et al [13]. In this process, a solid-state reaction between ZrO 2 and WC was used, and ZrC powder was added to adjust the microstructure.…”

Thermodynamic stability of in situ W–ZrC and W–Zr(CN) composites

“…Nano-sized ZrC synthesized through carbothermal reduction reduces the carbide size [12] and the dispersion of agglomerated ZrC powder gives a uniform microstructure [13]. Other methods for obtaining homogeneous dispersions of carbides include reactive melt penetration [14], infiltration [15], and in situ reactions [10]. However, none of these methods yet provides satisfactory composites [2,16].…”

“…Conventional powder metallurgy is most commonly employed to produce WeZrC composites from powder mixtures of W and zirconium carbides. However, the inherent tendency of ZrC to agglomerate and coarsen in the W matrix remains a drawback to this method, and results in the inadequate performance of the resulting composites at high temperatures [2,10,11].…”