OJCM  Vol.2 No.1 , January 2012
Influence of Nanocrystalline ZrO2 Additives on the Fracture Toughness and Hardness of Spark Plasma Activated Sintered WC/ZrO2 Nanocomposites Obtained by Mechanical Mixing Method
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/m1/2 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.
Cite this paper: M. El-Eskandarany, H. Soliman and M. Omoric, "Influence of Nanocrystalline ZrO2 Additives on the Fracture Toughness and Hardness of Spark Plasma Activated Sintered WC/ZrO2 Nanocomposites Obtained by Mechanical Mixing Method," Open Journal of Composite Materials, Vol. 2 No. 1, 2012, pp. 1-7. doi: 10.4236/ojcm.2012.21001.

[1]   M. S. El-Eskandarany, “Mechanical Alloying for Fabrication of Advanced Engineering Materials,” William Andrew, New York, 2001, p. 45.

[2]   T. Venkateswaran, D. Sarkar and B. Basu, “Tribological Properties of WC-ZrO2 Nanocomposites,” Journal of the American Ceramic Society, Vol. 88, No. 3, 2005, pp. 691- 697. doi:10.1111/j.1551-2916.2005.00129.x

[3]   M. S. El-Eskandarany, “Fabrication of Nanocrystalline WC and Nanocomposite WC-MgO Refractory Materials at Room Temperature,” Journal of Alloys and Compounds, Vol. 296, No. 1-2, 2000, pp. 175-182. doi:10.1016/S0925-8388(99)00508-3

[4]   M. S. El-Eskandarany, A. A. Mahday, H. A. Ahmed and A. H. Amer, “Synthesis and Characterizations of Ball- Milled Nanocrystalline WC and Nanocomposite WC-Co Powders and Subsequent Consolidations,” Journal of Alloys and Compounds, Vol. 312, No. 1-2, 2000, pp. 315- 325. doi:10.1016/S0925-8388(00)01155-5

[5]   H.-C. Kim, I.-J. Shon, J.-K. Yoon and J.-M. Doh, “Consolidation of Ultra Fine WC and WC-Co Hard Materials by Pulsed Current Activated Sintering and Its Mechanical Properties,” International Journal of Refractory Metals & Hard Materials, Vol. 25, No. 1, 2007, pp. 46-52. doi:10.1016/j.ijrmhm.2005.11.004

[6]   M. Sherif El-Eskandarany, M. Omori, T. Hirai, T. J. Konno, K. Sumiyama and K. Suzuki, “Synthesizing of Nanocomposite WC/MgO powders by Mechanical Solid- State Reduction and Subsequent Plasma-Activated Sintering,” Metallurgical and Materials Transactions A, Vol. 32, No. 1, 2001, pp. 157-164. doi:10.1007/s11661-001-0111-0

[7]   B. Basu, T. Venkateswaran and D. Sakar, “Pressureless Sintering and Tribological Properties of WC-ZrO2 Composites,” Journal of the European Ceramic Society, Vol. 25, No. 9, 2005, pp. 1603-1610. doi:10.1016/j.jeurceramsoc.2004.05.021

[8]   M. S. El-Eskandarany, “Fabrication and Characterizations of New Nanocomposite WC/Al2O3 Materials by Room Temperature Ball Milling and Subsequent Consolidation,” Journal of Alloys and Compounds, Vol. 391, No. 1-2, 2005, pp. 228-235. doi:10.1016/j.jallcom.2004.08.064

[9]   M. S. El-Eskandarany, M. Omori and A. Inoue, “Solid- State Synthesis of New Glassy Co65Ti20W15 Alloy Powders and Subsequent Densification into a Fully Dense Bulk Glass,” Journal of Materials Research, Vol. 20, No. 10, 2005, pp. 2845-2853. doi:10.1557/JMR.2005.0344

[10]   G. R. Anstis, P. Chantikul, B. R. Lawn and D. B. Marshall, “A Critical Evaluation of Indentation Techniques for Measuring Fracture Toughness: I, Direct Crack Meas- urements,” Journal of the American Ceramic Society, Vol. 64, No. 9, 1981, pp. 533-538. doi:10.1111/j.1151-2916.1981.tb10320.x

[11]   B. Basu, J. Vleugels and O. Van-der Biest, “Processing and Mechanical Properties of ZrO2-TiB2 Composites,” Journal of the European Ceramic Society, Vol. 25, No. 16, 2005, pp. 3629-3637. doi:10.1016/j.jeurceramsoc.2004.09.017

[12]   H. Miyazaki, Yu-ichi Yoshizawa and K. Hirao, “Effect of the Volume Ratio of Zirconia and Alumina on the Mechanical Properties of Fibrous Zirconia/Alumina Bi-Phase Composites Prepared by Co-Extrusion,” Journal of European Ceramics Society, Vol. 26, No. 16, 2006, pp. 3539-3546.

[13]   R. C. Garvie, R. H. Hannink and R. T. Pascoe, “Ceramic steel?” Nature, Vol. 258, No. 5537, 1975, pp. 703-704. doi:10.1038/258703a0

[14]   M. S. El-Eskandarany, M. Omori, M. Ishikuro, T. J. Kon- no, K. Takada, K. Sumiyama, T. Hirai and K. Suzuki, “Synthesis of Full-Density Nanocrystalline Tungsten Carbide by Reduction of Tungstic Oxide at Room Temperature,” Metallurgical and Materials Transactions A, Vol. 27A, No. 12, 1996, pp. 4210-4213. doi:10.1007/BF02595669