Effect of SiC nano-whisker addition on WC-Ni based cemented carbides fabricated by hot-press sintering

Ultrafine WC-Ni based cemented carbides with varying fraction of SiC nano-whiskers were fabricated by hot-press sintering at 1400 degrees C for 60 mm under a sintering pressure of 20 MPa and with the assistance of VC and TaC as WC grain growth inhibitors. X-ray diffraction analysis reveals that no SiC phase can be detected. Scanning electron microscopy examination indicates that the sintered samples have WC grains with a mean size of about 400 nm; with small amount of SiC nano-whisker, the samples can be consolidated; but as the added fraction of SiC nano-whisker increases, the agglomeration and inhomogeneous dispersion of the SiC whisker become more and more serious. With increasing added fraction of SiC nano-whisker, the flexural strength and Vickers hardness of the samples first increase and then decrease, indicating that an appropriate addition amount of SiC nano-whisker could improve the mechanical properties of the samples. When the SiC nano-whisker added fraction is 0.53 wt.% and 0.42 wt.%, the flexural strength and Vickers hardness of the samples reach their maximum values of about 1700 MPa and 1910 HV, respectively. The fracture toughness of the samples reaches its highest value of 15 MPa.m(1/2) when the added fraction of SIC nano-whisker is 0.53 wt.%. (C) 2012 Elsevier Ltd. All rights reserved.