Pico-Second Laser Micro Hole Drilling of Ceramics and Ceramic Matrix Composites

本项目的目标是开发一种高精度和高通量的加工陶瓷和陶瓷基复合材料(如碳化硅、氮化硅和碳化硅-碳化硅陶瓷基复合材料)深微孔的工艺。实现这一目标的途径将包括：i)建立使用最先进的皮秒激光进行高深宽比微孔钻孔的实验装置，ii)发展皮秒激光与材料相互作用的分析和数值模型，iii)实验研究确定参数对利用皮秒激光系统对陶瓷和陶瓷基复合板进行微孔钻孔的影响，以及iv)展示这些材料的微孔钻孔能力。先进材料，如陶瓷和陶瓷基复合材料，由于其优越的机械和热性能，对于国防、医疗、航空航天和商业工业具有重要的战略意义。许多由这些材料制成的零件需要精密的微孔来冷却和其他目的。然而，这些材料不适用于传统的微细加工工艺，如刻蚀或电火花加工，而常用的纳秒激光打孔的主要缺点是在激光烧蚀过程中造成表面热损伤。这种激光加工技术将克服目前在制造这些微孔方面的障碍，因为它可以通过直接将固体转化为等离子体来去除材料，几乎没有热损伤，从而由于极短的脉冲持续时间而产生所谓的“冷烧蚀”。应该可以在倾斜的曲面上形成一个干净的孔。由于该项目寻求通过分析和实验调查相结合的方式建立皮秒钻探过程的系统和科学模型，这项研究将产生关于超短激光与物质相互作用的关键科学知识。对超短脉冲激光与材料相互作用的深入了解将有助于激光加工领域的全面进步。一旦开发出来，这一工艺可以显著降低在许多难以加工的先进材料上制造微孔的成本，并提高这些材料在商业和军事产品中的利用率。

The objective of this project is to develop an accurate and high throughput process for machining deep micro holes in ceramics and ceramic matrix composites, such as silicon carbide, silicon nitride and silicon carbide-silicon carbide ceramic matrix composite. The approach to achieve this goal will include i) establishment of an experimental set-up for high aspect ratio micro hole drilling using a state-of-the-art pico-second laser, ii) development of analytical and numerical models for the pico-second laser and material interaction, iii) experimental studies to determine the effects of parameters on micro drilling of ceramic and ceramic matrix composite sheets using the pico-second laser system and iv) demonstration of micro hole drilling capabilities for these materials.Advanced materials such as ceramics and ceramic matrix composites are strategically important for the defense, medical, aerospace and commercial industries due to their superior mechanical and thermal properties. Many parts made of these materials require precision micro holes for cooling and other purposes. However, these materials are not amenable to conventional micro fabrication processes such as etching or electric discharge machining, while the major shortcoming of laser hole drilling by commonly used nanosecond lasers has been the surface thermal damage caused during laser ablation. This laser machining technique will overcome the current barriers in producing these micro holes, since it can remove the material with virtually no thermal damage by directly transforming solid to plasma and thus creating so called "cold ablation" due to the extremely short pulse duration. It should be possible to produce a clean hole on a curved surface in an oblique angle. Since the project seeks to develop a systematic and scientific model of the pico-second drilling process through combined analytical and experimental investigations, the research will generate critical scientific knowledge on ultra short laser-matter interaction. An improved understanding of ultra short pulse laser-material interaction will contribute to the overall advancement of the laser processing field. Once developed, this process can bring a significant cost reduction in producing micro holes on many difficult-to-machine advanced materials and increased utilization of those materials in commercial and military products.