Abrasive waterjet cutting of polycrystalline diamond: A preliminary investigation

Although abrasive waterjet (AWJ) machining has been employed in different setups (e.g. through cutting, milling, turning, cleaning) to generate surfaces in various workpiece materials (e.g. metallic alloys, ceramics, composites), up to now there is scarce information on the use of this technology in cutting super-hard materials such as diamond-based materials. The paper reports for the first time on a preliminary study of the capability of AWJ cutting of polycrystalline diamond (PCD) using abrasive media with different hardness, i.e. aluminium oxide (Al₂O₃), silicon carbide (SiC) and diamond. While keeping some operating parameters constant (pump pressure, stand-off distance and size of abrasives) the feed speed has been adjusted to enable full jet penetration for each type of abrasives. It was found that not only the material removal rates vary significantly with the employment of different types of abrasives but also the nozzle wear ratios, with further implications on the kerf quality (width, taper angle) of diamond cut surfaces. Furthermore in-depth studies of the cut surfaces helped to reveal the material removal mechanism when different types of abrasives are employed: Al₂O₃-low intensity erosion; SiC-medium erosion with undesired cracking; diamond-high intensity erosion. The experimental results showed that while Al₂O₃ and SiC abrasive media yield modest material removal rates (comparable with those obtained by electro discharge machining-EDM) the use of diamond abrasives can greatly increase (>200 times) the productivity of AWJ through cutting of PCD test pieces at acceptable roughness (Ra<1.6 μm) and integrity (i.e. crack-free) of the cut surfaces. Despite some limitations (e.g. cost of diamond abrasives, extensive nozzle wear rates) that can be overcome through further developments, it is believed that this preliminary research gives an indication of the capability of the AWJ to profile diamond-based structures for high-value engineering applications where conventional methods (e.g. EDM, laser) cannot be applied or are not productive enough.