Influence of starting WC particle size and sintering conditions on structure and properties of WC-Ni-Co coarse grain ceramics

Abstract

Sintering temperature is the key factor affecting the structure and performance of tungsten carbide (WC) ceramics. Thus, the effect of sintering temperature on the microstructure and mechanical properties of WC-Ni-Co coarse grain ceramics, obtained from the mixture containing: 60wt.% of ultra-coarse WC, 30 wt.% of fine WC, 7 wt.% of Co and 3wt.% of Ni powders, was analysed. The mechanical properties of WC ceramics did not change much when the sintering temperature was varied between 1410 and 1430 °C and the comprehensive performances of the ceramics were the best in this temperature range. In order to confirm that the coarse grain WC-Ni-Co ceramics can be applicable for harsh environments, it was compared with the standard WC-Co ceramics of the same grain size, and the reasons and mechanisms for the differences in microstructure and properties between the two ceramics were tested and analysed. The study shows that the average grain size of two ceramics does not differ much, and there are no decarburisation, graphite-phase and other impurity phases inside the ceramics. In addition, the difference in the mechanical properties is also small. However, the addition of Ni effectively improves the corrosion resistance of the WC-Co ceramics. Therefore, WC-Ni-Co can replace WC-Co ceramics as shield cutting tool material with the same grain size.

Keywords

• wc-ni-co ceramics
• grain coarsening
• microstructure
• mechanical properties
• wear resistance