Focused ion beam tomography of WC-Co cemented carbides

Abstract

The microstructure of three different grades of WC-Co cemented carbides (hardmetals) has been reconstructed in three dimensions after sequential images obtained by focused ion beam. The three dimensional microstructual parameters are compared against the well-known two dimensional parameters of grain size, phase percentages and mean free path. Results show good agreement with the exception of individual grain recognition, which could not be univocally segmented. In the case of mean free path, the three-dimensional image depicts a more realistic description of the metal interconnections in the composite. Aiming for a simple example of direct application of these FIB tomography outcomes, reconstructed real microstructure for the coarser hardmetal grade studied was translated in a finite element modelling mesh, and elastic residual stresses were estimated from sintering to room temperature. Calculated thermal stresses agree with experimental results and show significant local variations in their value due to the complex microstructure of cemented carbides.