US-Sweden Planning Visit: Laser/Waterjet Processing of Cubic and Wurtzite Boron Nitride to Exceed the Hardness of Diamond

该项目将启动美国爱荷华州立大学和瑞典隆德大学的研究人员之间的一项新的国际合作，设计比钻石更硬、化学性质更稳定的微结构材料。这种材料可能有许多工业应用，特别是在加工工具中。单晶和多晶金刚石是已知最硬的材料；然而，在高温下，金刚石失去了其化学惰性和热稳定性。相比之下，立方氮化硼（cBN）具有优异的化学和热稳定性，但硬度低得多。将BN的硬度提高到金刚石的水平，有望使BN材料在腐蚀性和高温环境中优于金刚石基工具材料。与目前最先进的金刚石工具相比，超硬合成氮化硼材料具有优越的化学和热稳定性，因此其开发和成本效益高的加工有可能彻底改变制造业。例如，使用最硬的BN工具对淬火钢模具进行超精密加工，可以产生光学质量表面和超细公差，从而在提高形状精度的同时消除昂贵的抛光操作。本次计划访问将探索一种新型激光/水射流工艺对两相立方氮化硼/纤锌矿氮化硼材料（cBN/wBN）的影响，以确定该处理是否会导致BN超过金刚石的硬度。激光/水射流工艺是由爱荷华州立大学与隆德大学的研究人员合作开发的，隆德大学是立方/纤锌矿型氮化硼合成和表征方面的领先专家。预计此次计划访问将启动一些不同的研究方向，包括设计能够产生所需显微组织以提高硬度的加工条件，了解激光加热和水射流淬火对cBN/wBN显微组织的影响，评估超硬BN刀具材料对铁合金高速加工的影响。确定BN微观结构如何影响cBN/wBN的化学和力学性能。总的来说，这项合作研究工作将使人们更好地理解超硬材料的结构-性能相关性。这笔拨款将支持PI、Shrotriya和一名美国研究生的计划访问。研究生将在瑞典花费大约一个月的时间进行概念验证研究，这可能会导致向工程理事会的土木，机械和制造创新部门以及数学和物理科学理事会的材料研究部门提出更大的研究建议。

This project will initiate a new international collaboration between researchers at Iowa State University, USA and Lund University, Sweden to design micro-structured materials that are harder than diamond and also more chemically stable. Such materials are likely to have numerous industrial applications, especially in machining tools. Single and polycrystalline diamonds are the hardest known materials; however, at high temperatures, diamond loses its chemical inertness and thermal stability. In contrast, cubic boron nitride (cBN) has exceptional chemical and thermal stability but has much lower hardness. Increasing the hardness of BN to the level of diamond is expected to allow BN materials to outperform diamond-based tool materials in corrosive and high temperature environments. The development and cost-effective processing of ultra-hard synthetic BN has the potential to revolutionize the manufacturing industry because of the superior chemical and thermal stability of BN materials compared to current state-of-art diamond tools. For example, ultra-precision machining of hardened steel dies and molds using the hardest BN tool could produce optical quality surfaces and ultra-fine tolerances, allowing expensive polishing operations to be eliminated while improving form accuracy. This planning visit will explore the effects of a novel laser/waterjet process on two phase cubic boron nitride/wurtzite boron nitride materials (cBN/wBN) to determine if the treatment leads to BN that exceeds the hardness of diamond. The laser/waterjet process was developed at Iowa State University in collaboration with researchers at Lund University who are leading experts in synthesis and characterization of cubic/wurtzite Boron Nitride. The planning visit is expected to initiate work on a number of different research directions, including designing processing conditions that result in desired microstructures for hardness enhancement, understanding the effects of laser heating and waterjet quenching on microstructures in cBN/wBN, assessing the influence of ultra-hard BN tool materials on high speed machining of ferrous alloys, and determining how the BN microstructures influence the chemical and mechanical properties of cBN/wBN. Overall this collaborative research effort will enable greater understanding of structure-property correlations in ultra-hard materials.The grant will support a planning visit by the PI, Shrotriya, and a US graduate student. The graduate student will spend approximately a month in Sweden performing proof of concept research that is likely to result in developing larger research proposals to the NSF division of Civil, Mechanical and Manufacturing Innovation in the Engineering directorate as well as the Division of Materials Research in the Math and Physical Sciences Directorate.