Surface Integrity Analysis of Ceramics Machined by Wire EDM Using Different Trim Cut Technologies
Surface Integrity Analysis of Ceramics Machined by Wire EDM Using Different Trim Cut Technologies
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DOI：
10.1016/j.procir.2020.02.026
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发表时间：
2020
期刊：
影响因子：
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通讯作者：
T. Bergs;M. Olivier;A. Gommeringer;F. Kern;A. Klink
中科院分区：
文献类型：
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作者：
T. Bergs;M. Olivier;A. Gommeringer;F. Kern;A. Klink
导电陶瓷由于其高的耐热性和耐化学性，越来越多地应用于模具和化学工业。这种材料的高硬度是传统制造工艺面临的主要挑战。电火花线切割加工（WEDM）提供了一个很好的选择，因为加工过程与硬度无关。然而，电火花线切割的热材料去除原理导致近表层的微观结构发生变化，从而影响材料的承载能力。为了尽量减少这些损害并增加承重能力，必须使用修剪切割。目前，电火花切割机床上还没有加工导电陶瓷的加工技术。因此，本研究通过开发一种具有主切割和切边切割的材料专用技术来改善氧化锆/碳化钨（TZP-WC）作为导电陶瓷的表面完整性。通过表面粗糙度测量、截面分析和弯曲强度试验，验证了表面改进的有效性。主要的材料去除机制被确定为熔化，蒸发和剥落。这导致光滑但玻璃表面。电火花加工特性的变化引起了表面结构的变化。然而，放电能量对表面状态和去除机制都有很大的影响。通过创建光滑且几乎无裂纹的边缘区域，可以实现超过900兆帕的弯曲强度。具有较高放电能量的修剪切割会对表面造成致命的损伤，并导致弯曲强度的破坏。
Electrically conductive ceramics are increasingly used in tooling and chemical industry, because of their high thermal and chemical resistance. The high hardness of the material is a major challenge for conventional manufacturing processes. Wire electrical discharge machining (WEDM) offers a good alternative, because the machining process is independent of the hardness. Nevertheless, the thermal material removal principle of WEDM leads to a microstructure change in the near-surface layer, which affects the load-bearing capacity of the material. In order to minimize these damages and to increase the load-bearing capacity, trim cuts must be used. Up to now, there are no processing technologies available on WEDM-machines for machining electrically conductive ceramics. Therefore, this study deals with the surface integrity improvement of zirconia/tungsten carbide (TZP-WC) as an electrically conductive ceramic by developing a material-specific technology with main and trim cuts. The surface improvement is verified by means of surface roughness measurements, cross-section analysis and bending strength tests. The dominant material removal mechanisms were identified to be melting, evaporation and spalling. This leads to smooth but glassy surfaces. The variation of the EDM characteristics caused a variation in the structure of the resulting surface. However, the discharge energy has a strong impact on both surface condition and removal mechanism. Bending strengths of over 900 MPa could be achived by creating a smooth and nearly crack-free rim zone. Trim cuts with higher electrical discharge energies cause fatal damage in the surface and lead to a breakdown of the bending strength.