Novel Processing of WC/Co Hardmetals with Simultaneous Improvements in Hardness and Toughness Derived From Nanocrystalline Powder

WC/Co 硬质合金的新颖加工，同时提高纳米晶粉末的硬度和韧性

• 批准号: 0856122
• 负责人: Leon Shaw
• 金额: $ 30万
• 依托单位: University of Connecticut
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-01 至 2013-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0856122&HistoricalAwards=false
• 关键词: Novel; Processing; WC; Co; Hardmetals

The research objective of this award is to develop innovative manufacturing methods that can produce novel materials derived from nanocrystalline powder with low costs and superior mechanical properties simultaneously. Specifically, a novel manufacturing process, termed as the Integrated Mechanical and Thermal Activation (IMTA) process, will be utilized to make low cost nanostructured WC/Co powder which will subsequently be densified using the innovative sintering strategy to allow the conversion of nano-WC particles to submicrometer-sized WC platelets. The dense WC/Co cermets with submicrometer-sized WC platelets are expected to offer unprecedented simultaneous improvements in hardness and toughness. To achieve the best improvements, WC platelets will be fabricated to have both high aspect ratio and thin thickness. The thin thickness will limit the slip distance of dislocations and thus provide high hardness, while the high aspect ratio of platelets will offer effective crack deflection and thus result in high toughness. Thin and high aspect ratio WC platelets will be produced via detailed and comprehensive studies of the effects of sintering conditions, the size of the starting WC particles, the Co concentration, the free carbon concentration, and addition of a small amount of dopants. The microstructure of WC/Co with and without doping sintered under various conditions will be characterized in detail to elucidate the formation mechanism of WC platelets and the effect of various dopants and processing conditions. Deliverables include mechanistic understanding of the effects of sintering conditions, the size of the starting WC particles, the Co concentration, the free carbon concentration, and a small amount of dopants on the formation of WC platelets, dense WC/Co cermets with simultaneous improvements in hardness and toughness, engineering students education, and research experience for middle/high school underrepresented minority students.If successful, the results of this research will produce a new generation of low cost and high performance WC/Co cermets with superior hardness and toughness for advanced structural applications by many industries. These novel WC/Co cermets could also open up new opportunities in areas outside their current application windows. The understanding developed from this research will lay a scientific foundation for enhancing anisotropic growth of crystals and can be applied directly to other hardmetals such as WC-Ni, WC-NiCo, and WC-CoCr. The scientific principles discovered can also shed light on the processing and microstructure design of advanced ceramics with the anisotropic grain growth property (e.g., Ti3SiC2, Ti3AlC2, and liquid-phase-sintered Si3N4, SiC and Al2O3). Graduate and undergraduate engineering students will benefit from this project through classroom instruction and involvement in the research. Through specially designed summer programs, middle/high school underrepresented minority students will participate in the research. These summer programs will nurture underrepresented minorities towards positive thinking, increase their interest in science and technology, and motivate them to pursue higher education and become future leaders of the society.

该奖项的研究目标是开发创新的制造方法，可以同时生产低成本和上级机械性能的纳米晶粉末衍生的新型材料。具体而言，一种新的制造工艺，称为集成机械和热活化（IMTA）工艺，将用于制造低成本的纳米结构WC/Co粉末，随后将使用创新的烧结策略进行致密化，以允许将纳米WC颗粒转化为亚微米尺寸的WC片晶。具有亚微米尺寸WC片晶的致密WC/Co金属陶瓷有望同时提供前所未有的硬度和韧性改善。为了实现最佳的改进，WC片晶将被制造成具有高纵横比和薄厚度。薄的厚度将限制位错的滑移距离，从而提供高硬度，而薄片的高纵横比将提供有效的裂纹偏转，从而导致高韧性。通过对烧结条件、起始WC颗粒的尺寸、Co浓度、游离碳浓度和添加少量掺杂剂的影响进行详细和全面的研究，将生产薄且高纵横比的WC片晶。通过对不同烧结条件下掺杂和未掺杂WC/Co的微观结构进行详细表征，阐明WC片晶的形成机理以及各种掺杂剂和工艺条件的影响。可获得的成果包括对烧结条件、起始WC颗粒的尺寸、Co浓度、游离碳浓度和少量掺杂剂对WC片晶形成的影响的机械理解、同时提高硬度和韧性的致密WC/Co金属陶瓷、工程专业学生教育以及针对初中/高中少数民族学生的研究经验。如果成功，本研究的结果将产生新一代低成本和高性能的WC/Co金属陶瓷，其具有上级硬度和韧性，可用于许多工业的高级结构应用。这些新型WC/Co金属陶瓷还可以在其当前应用窗口之外的领域开辟新的机会。从这项研究中获得的认识将为增强晶体的各向异性生长奠定科学基础，并可直接应用于其他硬质合金，如WC-Ni，WC-NiCo和WC-CoCr。所发现的科学原理也可以阐明具有各向异性晶粒生长特性的先进陶瓷的加工和微观结构设计（例如，Ti 3SiC 2、Ti 3AlC 2和液相烧结的Si 3 N4、SiC和Al 2 O3）。研究生和本科工程专业的学生将通过课堂教学和参与研究从这个项目中受益。通过专门设计的暑期项目，初中/高中代表性不足的少数民族学生将参加研究。这些暑期项目将培养少数民族的积极思维，提高他们对科学和技术的兴趣，并激励他们接受高等教育，成为社会的未来领导者。