Performance of Different CVD Diamond-Coatings and Substrate Materials in Cutting of Tungsten Carbide With Laser-Treated Tools

Tungsten carbide is an important material for manufacturing cutting tools, molds and dies due to its combination of high hardness and high resistance to mechanical loads and wear. The main limitation for using this material is the time-consuming and costly machining process due to its low machinability. Diamond-coated carbide tools have shown promising results, allowing process-reliable milling of tungsten carbide as an alternative to conventional electro discharge machining. In application of these cutting tools, a flaking of the coating on the rake face occurs. The coating on the flank face remains undamaged and acts as new cutting edge. Since the undeformed chip thickness is smaller than the thickness of the diamond coating, the tools remain useable. Due to the flaking of the coating, the cutting edge radius and the effective rake angle are reduced. A self-sharpening effect occurs, which results in improved cutting conditions. The findings of this study demonstrate that, regardless of the type of coating and the choice of substrate material, a coating flaking on the rake face occurred. This flaking led to a reduction of the cutting force components and tool temperature. A recreation of this coating flaking by removing the coating on the rake face using a laser increased the obtained tool life. Thermal and mechanical load were lowered, and the scatter of the measured values decreased. In comparison of different tool concepts, the grain size of the substrate material was identified as a critical factor influencing tool life. Irrespective of the coating selected, the tools with fine grain size substrate material exhibited a longer tool life due to improved coating adhesion. For the tested coatings, no discernible influence of the tool life was identified.