Evaluating the Hardness of Yttrium Ruthenium Borides

High hardness materials are used for a multitude of applications, ranging from drill bits and saw blades to artificial joint replacement. Most of these materials are constructed out of simple binary phases, namely transition metal borides and carbides. Their simplicity makes them easy to produce but limits the ability to tune the mechanical properties through chemical substitution. As a result, we are investigating ternary borides that may have high hardness. The project started by preparing three yttrium ruthenium borides (YRu3B2, YRu4B4, YRuB4). The powders were mixed and pressed into pellets that were then melted into homogeneous ingots using an arc-melter under an argon atmosphere. After optimising the reaction conditions, the samples are ground, and the sample purity is checked using powder X-ray diffraction. The samples’ resistances to plastic deformation are measured with the Vickers hardness test under different loads. Density functional theory calculations were then used to understand how changes in electron density as a function of chemical composition could be used to maximise the mechanical properties. We are now using this information to develop new ternary high hardness materials with even better mechanical properties.