Experimental study on aluminium to tungsten carbide/polycrystalline diamond (WC/PCD) adhesive bonding for milling tools

Nowadays the use of adhesives is deeply embedded in the modern automotive and aeronautical industries. However, in other areas, such as the milling tool sector, it is still a quite unexplored technology. This work studies the adhesive bonding process between aluminium and WC/PCD, both commonly used in woodworking milling tools. To allow for electric discharge machining (EDM) as a sharpening process, an electrically conductive adhesive combined with conductive microspheres was used. Bulk tensile tests, thick adherend shear tests (TAST), double cantilever beam (DCB) tests and end notched fracture (ENF) tests were used to mechanically characterise the adhesive. The joining process was studied using small-scale single lap joint (SLJ) specimens manufactured with three v/v% of spheres - 0%, 5% and 10%. The need for surface treatments was evaluated by measuring the surface energy of the substrates, applying then the necessary procedures. And the electrical resistance of the studied joints was measured with the four-probe method. It was found that with the increase in v/v% of spheres both the electrical resistance and strength decreased. However, when looking for a good compromise between both mechanical and electrical properties, the results point towards the 5% spheres content. To finalise this study, the previously detailed adhesive characterisation was performed once again for the chosen v/v% of spheres, showing a reduction in fracture toughness, as expected.