Abstract

The present study reports the formation of ultrafine hard particles of nanocomposite WC with different additions of ZrO₂ powders (0.5 - 20 vol.%). The initial mixed powders of WC with the desired ZrO₂ concentrations were mechanically mixed for 360 ks (end-product) under argon gas atmosphere at room temperature, using high energy ball mill. The end-product consists of average grain size of about 17 nm in diameter. The obtained nanocomposite powders were consolidated into fully dense compact, using spark plasma sintering (SPS) technique in vacuum. The experimental results revealed that the consolidation step, which was conducted at 1673 K with uniaxial pressure ranging from 19.6 to 38.2 MPa for short time (0.18 ks), does not lead to dramatic grain growth in the powders so that the consolidated nanocomposite bulk objects maintain their nanocrystalline behavior, being fine grains with an average size of 63 nm in diameter. The relative densities of consolidated nanocomposite WC/ZrO₂ materials increase from 99.1% for WC-0.5% ZrO₂ to 99.93% for WC-20% ZrO₂. The indentation fracture toughness of the composites can be tailored between 7.31 and 19.46 MPa/m^1/2 by controlling the volume fraction of ZrO₂ matrix from 0.5% to 20%. The results show that the Poisson’s ratio increased monotonically with increasing the ZrO₂ concentrations to get a maximum value of 0.268 for WC-20% ZrO₂. In the whole range of ZrO₂ concentrations (0.5 - 20 vol.%), high hardness values (20.73 to 22.83 GPa) were achieved. The Young’s modulus tends to decrease with increasing the volume fraction of the ZrO₂ matrix to reach a minimum value of 583.2 GPa for WC-20% ZrO₂. These hard and tough WC/ZrO₂ nanocomposites are proposed to be employed as higher abrasive-wear resistant materials.

Keywords

Nanocomposite; Tungsten Carbide; Zirconia; Spark Plasma Sintering; Powder Metallurgy; Mechanical Alloying; Microstructure; SEM, HRTEM

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Conflicts of Interest

The authors declare no conflicts of interest.

References