Analysis on carbonization evolution behavior of tungsten carbide powders and its application in cutting tools

Abstract

In this article, the microstructural evolution of tungsten carbide (WC) powder with coarse particle size was studied. The WC powders were prepared by directly carbonizing tungsten powders of 8.5 μm in Fisher sub-sieve size (FSSS) under various conditions. The sequence of chemical reactions was analyzed by calculating the Gibbs free energies, and the phase transition mechanisms of tungsten particles was studied by using characterization techniques including SEM and XRD. The experimental results showed that the phase transition process is dominated by carbon diffusion reaction, and the diffusion rate was studied by analyzing carbonized tungsten particles prepared at specific temperatures. The grain growth process and mechanism were also studied by analyzing the morphology and grain size of WC powders prepared at 1800 °C in different carbonization times, and the results are consistent with the recrystallization grain growth theory. Finally, technique of Electron Backscattered Diffraction (EBSD) was utilized to identify and measure the grain size of WC powders prepared from tungsten powder of 0.6 μm in FSSS. The cemented tungsten carbide substrate prepared from WC powder with higher average grain size exhibited higher performances in metal cutting application of turning and drilling.