Mechanical strength assessment of single WC-WC interfaces present in WC-Co hardmetals through micro-beam bending experiments

Recently, there have been significant efforts to develop micro-mechanical models for a better understanding of in-service performance of WC-Co components. However, reliable information about the mechanical properties of individual features like grains or interfaces is still lacking. In this work, micro-beam testing has been used for analyzing the fracture strength of different WC-WC interfaces in a WC-6.5 wt%Co alloy. The method is based on machining cantilever beams by using Focused Ion Beam so that a single WC-WC interface is isolated from the rest of the microstructure. This machining is carried out in order to have the selected interface at a certain distance for the fixed end and perpendicular to the cantilever axis. CSL2 boundaries and randomly oriented boundaries have been identified by means of EBSD and subsequently tested by nanoindentation until fracture. Load-displacement curves confirm that CSL2 boundaries are stronger than the others and post mortem analyses indicates that the fracture mechanisms are different depending on the orientation between adjacent WC grains. This approach could be used to investigate the intrinsic strength of other interfaces present in hardmetals (i.e. WC/Co, FCC carbides/Co, FCC carbides/WC) and how it is related with processing parameters or in-service conditions.