Micropillar compression of single crystal tungsten carbide, Part 1: temperature and orientation dependence of deformation behaviour

TL;DR

This study investigates how temperature and crystal orientation influence the deformation mechanisms of single crystal tungsten carbide micropillars, revealing anisotropic plasticity and temperature-dependent softening relevant for cutting tool performance.

Contribution

It provides new insights into the orientation-dependent deformation behavior and mechanisms of WC at micro-scale under various temperatures, using focused ion beam fabricated micropillars.

Findings

Flow stresses vary significantly with orientation.

Deformation mechanisms are orientation and temperature dependent.

Prismatic slip dominates at room temperature, basal slip activates at higher temperatures.

Abstract

Tungsten carbide cobalt hardmetals are commonly used as cutting tools subject to high operation temperature and pressures, where the mechanical performance of the tungsten carbide phase affects the wear and lifetime of the material. In this study, the mechanical behaviour of the isolated tungsten carbide (WC) phase was investigated using single crystal micropillar compression. Micropillars in two crystal orientations, 1-5 ${\mu}$m in diameter, were fabricated using focused ion beam (FIB) machining and subsequently compressed between room temperature and 600 {\deg}C. The activated plastic deformation mechanisms were strongly anisotropic and weakly temperature dependent. The flow stresses of basal-oriented pillars were about three times higher than the prismatic pillars, and pillars of both orientations soften slightly with increasing temperature. The basal pillars tended to deform by either unstable cracking or unstable yield, whereas the prismatic pillars deformed by slip-mediated cracking. However, the active deformation mechanisms were also sensitive to pillar size and shape. Slip trace analysis of the deformed pillars showed that {10-10} prismatic planes were the dominant slip plane in WC. Basal slip was also activated as a secondary slip system at high temperatures.