Post-machining strategies for additively manufactured silicon carbide ceramic components

Abstract

Additive Manufacturing offers a high level of freedom in design. Higher functionality can be achieved through more complex shapes which can only be manufactured by 3D printing. To achieve the desired surface quality and dimensional accuracy, it is necessary to post-machine the components. In the case of 3D printed silicon carbide (SiC) ceramic components, machining becomes extremely challenging not only due to its high hardness and wear resistance but also due to its complex shape. Polycrystalline diamond tools with geometrically defined cutting edges are used to meet these challenges. To obtain these components, a thermoplastic compound is shaped using the extrusion-based 3D printing technology. The green body is transformed to a SiC-based ceramic using the Liquid Silicon Infiltration process. Different feedstocks lead to different microstructures. The phase compositions range from monolithic two-phase-material SiSiC (approx. 88 % SiC, 12 % silicon) to C-SiSiC with short carbon fibres (approx. 50 % SiC, 20 % carbon, 30 % silicon). These compositions not only affect (thermo-) mechanical properties but also subsequent machining processes. In order to overcome the high hardness and the challenges posed by the brittle behavior of SiC-based ceramics, machining with geometrically defined cutting edges is systematically investigated. For this purpose, machining tests are conducted in a linear-orthogonal cutting configuration. In this configuration, the macro geometry of the polycrystalline diamond tools and the cooling lubricant strategy are tested. 2D cutting simulations, employing a ceramic material model based on the Drucker-Prager criterion, complement the experimental findings. The collected results contribute to the machining of complex additively manufactured ceramic components.