Abstract
The effects of different reinforcement shapes on stability and repeatability of micro electrical discharge machining were experimentally investigated for ultra-high-temperature ceramics based on zirconium diboride (ZrB2) doped by SiC. Two reinforcement shapes, namely SiC short fibers and SiC whiskers were selected in accordance with their potential effects on mechanical properties and oxidation performance. Specific sets of process parameters were defined minimizing the short circuits in order to identify the best combination for different pulse types. The obtained results were then correlated with the energy per single discharge and the discharges occurred for all the combinations of material and pulse type. The pulse characterization was performed by recording pulses data by means of an oscilloscope, while the surface characteristics were defined by a 3D reconstruction. The results indicated how reinforcement shapes affect the energy efficiency of the process and change the surface aspect.
Highlights
Among the advanced ceramic materials, ultra-high-temperature ceramics (UHTCs) are characterized by excellent performances in extreme environments
The plot shows a lower energy efficiency for pulse type A and this is a positive aspect because it indicates less impact on the electrode wear
To evaluate the energy efficiency from the material removed point of view, as has already been done in the previous plot, the material removal per single discharge was evaluate as the ratio with the energy for single discharge
Summary
Among the advanced ceramic materials, ultra-high-temperature ceramics (UHTCs) are characterized by excellent performances in extreme environments. The relative density of the base material ZrB2 is usually about 85% because of the high level of porosity of the structure, in the last years, researchers are focused on fabricating high-density composites characterized by good strength (500–1000 MPa) For these reasons, the use of single-phase materials is not sufficient for high-temperature structural applications. An example is the addition of SiC, it has been widely proved that its addition improves the fracture strength and the oxidation resistance of ZrB2-based materials due to the grain refinement and the formation of a protective silica-based layer Based on these aspects, recent works have focused on ZrB2-based composites behavior generated by the addition of SiC with different shapes (e.g., whiskers or fibers). The critical aspect of the reinforced process was the reaction or the degeneration of the reinforcement during the sintering process [13,14]
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