The directional crystallization of W–B–C–d-transition metal alloys

Crystallization from the melt during arc melting and directional solidification during induction zone melting of pseudo-alloys tungsten carbide (WC)–MeB2 (Me—Ti, Zr, Cr) and a number of alloys of the W–B–C system (WB0.12C0.74; WB0.25C0.75; WB0.34C0.32; WB0.49C0.76; WB0.59C0.76; WB0.89C0.75; (WC)0.9B0.1) has been studied. It was shown that the alloys WC—80 mass%–ZrB2—20 mass% and WC—72 mass%–WB—28 mass% are the closest ones to eutectic compositions. Investigation of the microstructure of eutectic alloys in the WC–WB system by thin foil method has revealed that both matrix and reinforcing phases are single crystalline.Hardness tests by indentation of the eutectic structure area (P=10.3 N) do not result in radial crack formation, which is evidence of the essential plasticity of the obtained composite material. It is established that new ceramic–ceramic eutectic composite materials based on WC with transition metal diborides and with a boride phase of tungsten may be created. Such materials can be successfully applied in contemporary high-temperature techniques.

The eutectic structure in WC–WB system.Figure optionsDownload as PowerPoint slide