Fundamental investigations on the development of a single-phase CO2-lubricant solution to support deep-hole drilling processes for difficult to cut materials by using a cryogenic CO2 snow-lubricant-jet

高效的切屑排空和散热在加工镍基合金(如Inconel718)中起着重要作用。此外，对更高效的推进系统的需求不断增加，导致由难切割材料制成的部件的应用越来越多。例如，用于飞机和机动车辆发动机的材料的特点导致对生产系统的高要求。特别是，较差的散热性与较高的延展性、硬度和耐热性相结合，降低了切屑的易碎性，并导致了较高的工件和刀具材料的热负荷和机械负荷。由此，将少量润滑剂注入液化二氧化碳(CO2)气流中，以实现冷却和润滑效果。对于这项技术，有必要使用润滑剂，这种润滑剂可以少量溶解在液化的二氧化碳中，以防止润滑剂和二氧化碳分离。尽管使用这种技术可以在不提供高压技术的情况下结合传统MQL和湿法加工的优点，但对于制造过程中使用的润滑剂与液化二氧化碳之间的相互作用缺乏了解。在加工技术领域，钻削Inconel 718时的切屑形成、表面完整性、刀具寿命和磨损机理将是本研究项目的关键问题。对于流体力学，将研究选定的润滑剂与液化二氧化碳的相平衡、它们的溶液运动学以及在相变过程中溶液的行为。这个研究项目的结果将被用来获得关于使用cMQL的机制的一般知识。此外，基于这些结果，重点从经济和生态方面对加工过程进行了优化。因此，将观察cMQL对刀具寿命、工件和加工质量的影响。为了表征应用行为，将应用已建立的破坏性和非破坏性材料测试方法，这些方法是为检查深钻过程中的切屑形成和传输而开发的。此外，为了研究润滑剂在液化二氧化碳中的溶液行为，将研究确定溶液的相行为、流动运动学和雪花形成(雾化)的方法。因此，通过结合相关研究所在生产和工艺工程领域的专业知识，将在这一跨学科研究项目中开发一种应用cMQL的新方法，以显著提高MQL技术的工艺极限。因此，有了cMQL，就有可能同时利用MQL和洪水冷却的优点，在具有挑战性尺寸的难切割材料的钻孔过程中使用。

Efficient chip evacuation and heat dissipation takes an important role in machining of nickel based alloys, e.g. Inconel 718. Furthermore, an increasing demand for more efficient propulsion systems leads to a rising application of components, made from hard to cut materials. The characteristics of materials, which are used for instance in aircraft and motor vehicle engines, lead to high demands for production systems. In particular, a poor heat dissipation combined with a high ductility, hardness and heat resistance of the workpiece material decrease chip breakability and lead to high thermal and mechanical loads of workpiece and tool materials.This research project will focus on the promising approach to improve the chip evacuation and heat dissipation using cryogenic minimum quantity lubrication (cMQL). Thereby, a small amount of lubricant is injected into a liquefied carbon dioxide (CO2) stream to realize a cooling and lubricating effect. For this technique, it is necessary to use lubricants, which can be dissolved in small quantities in liquefied CO2 to prevent a separation of lubricant and CO2. There is a lack of knowledge in interaction between lubricants, which are used in manufacturing processes, and liquefied CO2 despite the fact that using this technology, the advantages of conventional MQL and wet machining can be combined without providing high pressure technologies.In the field of machining technologies, chip formation, surface integrity, tool life and wear mechanisms while drilling Inconel 718 will be key issues in this research project. For fluid mechanics, phase equilibrium of selected lubricants with liquefied CO2, their solution kinematics and behavior of the solution during the phase change liquid-gaseous will be examined. Results of this research project will be used to gain general knowledge about mechanisms using cMQL. Furthermore, based on these results optimization of machining processes with respect to economic and ecologic aspects is focused. Therefore, effects of cMQL on tool life, workpiece and process quality will be observed. To characterize the application behavior, established methods of destructive and non-destructive material testing, which were developed to examine chip formation and transport in deep drilling processes, will be applied. Furthermore, to investigate solution behavior of lubricants in liquefied CO2, methods for determining phase behavior of the solution, flow kinematics and snow jet formation (atomization) will be investigated.Thus, by combining expertise in the fields of production and process engineering of the involved institutes, a new methodology to apply cMQL will be developed in this interdisciplinary research project to significantly enhance process limits of MQL technique. Hence, with cMQL it will be possible to use advantages of both, MQL and flood cooling for drilling processes of hard to cut materials in challenging dimensions.