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，能够生产出源自纳米晶粉末的新型材料，同时具有低成本和优异的机械性能。具体来说，一种称为集成机械和热活化（IMTA）工艺的新型制造工艺将用于制造低成本纳米结构 WC/Co 粉末，随后使用创新的烧结策略将其致密化，以实现纳米 WC 的转化颗粒到亚微米尺寸的 WC 片晶。具有亚微米尺寸 WC 片晶的致密 WC/Co 金属陶瓷预计将在硬度和韧性方面实现前所未有的同步改进。为了实现最佳改进，WC 片晶将被制造为具有高纵横比和薄厚度。较薄的厚度将限制位错的滑移距离，从而提供高硬度，而片晶的高纵横比将提供有效的裂纹偏转，从而产生高韧性。通过对烧结条件、起始 WC 颗粒尺寸、Co 浓度、游离碳浓度以及添加少量掺杂剂的影响进行详细而全面的研究，将生产出薄而高长径比的 WC 片晶。将详细表征在各种条件下烧结的掺杂和不掺杂的 WC/Co 的微观结构，以阐明 WC 片晶的形成机制以及各种掺杂剂和加工条件的影响。可交付成果包括对烧结条件、起始 WC 颗粒尺寸、Co 浓度、游离碳浓度和少量掺杂剂对 WC 片状、致密 WC/Co 金属陶瓷形成的影响的机械理解，同时改进硬度和韧性、工科学生教育以及针对少数族裔学生的初中/高中研究经验。如果成功，这项研究的结果将产生新一代低成本高性能WC/Co具有卓越硬度和韧性的金属陶瓷，适用于许多行业的先进结构应用。这些新型 WC/Co 金属陶瓷还可以在其当前应用范围之外的领域开辟新的机会。这项研究得出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。发现的科学原理还可以为具有各向异性晶粒生长特性的先进陶瓷（例如Ti3SiC2、Ti3AlC2和液相烧结Si3N4、SiC和Al2O3）的加工和微观结构设计提供启示。工程专业的研究生和本科生将通过课堂教学和参与研究从该项目中受益。通过专门设计的暑期项目，代表性不足的少数族裔学生将参与研究。这些暑期项目将培养少数族裔积极思考，增加他们对科学技术的兴趣，并激励他们接受高等教育并成为社会未来的领导者。