A Fundamental Investigation of the Laser Engineered Net Shaping Process for the Fabrication of Nanostructured Cermets

这项资助的研究目标是研究激光工程净成形系统对纳米结构碳化钨钴金属陶瓷直接净成形制造的适用性，并对该工艺的热方面有一个基本的了解。这将通过制造简单和复杂形状的纳米结构碳化钨钴金属陶瓷来实现。这些样品的物理和机械性能，如显微硬度、屈服强度、抗拉强度和弹性模量，将被评估。受激光束影响的样品区域的原位温度表征将使用双波长成像高温计系统进行，该系统提供了沉积过程中热历史和由此产生的热应力的信息。x射线衍射将结合光学显微镜、扫描电镜、透射电镜和图像分析，表征纳米碳化钨颗粒在钴基体中的尺寸分布、体积分数和相分解，建立加工变量与颗粒尺寸、形状和分布之间的关系。为了评估纳米碳化钨颗粒的热稳定性及其与钴基体的相互作用，将使用不同的沉积参数。最后，将使用技术成本建模和生命周期评估技术，对经济和环境效益进行定量评估。如果成功，这项工作的好处将包括能够为工具、模具和喷嘴等产品制造具有更好机械性能的复杂形状。通过使用激光工程净成形系统，加工需求将被最小化，从而降低制造成本，减少废料产生的材料浪费，改善材料性能，提高工艺效率，缩短产品设计时间，减少环境污染。这项工作的结果也将进一步科学地理解纳米结构材料和网状成形技术。此外，将加强与工业和国家实验室的合作活动，并加强教育计划，包括那些代表性不足的少数民族的教育计划。

The research objective of this grant is to investigate the suitability of the Laser Engineered Net Shaping system for the direct net-shape fabrication of nanostructured tungsten-carbide-cobalt cermets and to develop a fundamental understanding of the thermal aspects of the process. This will be accomplished by making nanostructured tungsten-carbide-cobalt cermets in both simple and complex shapes. Physical and mechanical properties of these samples, such as microhardness, yield strength, tensile strength, and modulus of elasticity, will be evaluated. In-situ temperature characterization of the area of the sample affected by the laser beam will be conducted using a two-wavelength imaging pyrometer system, which provides information on the thermal history and the resulting thermal stresses during deposition. X-ray diffraction, in combination with optical microscopy, scanning electron microscopy, transmission electron microscopy and image analysis, will be used to characterize the size distribution, volume fraction and phase decomposition of nanosized tungsten carbide particles in the cobalt matrix, and to establish the relationship between processing variables and particle size, shape and distribution. Different deposition parameters will be used in order to assess the thermal stability of the nanosized tungsten carbide particles and its interaction with the cobalt matrix. Finally, the economic and environmental benefits will be quantitatively assessed, with the use of technical cost modeling and life cycle assessment techniques. If successful, the benefits of this work will include the ability to fabricate complex shapes with better mechanical properties for products such as tools, dies and nozzles. By using the Laser Engineered Net Shaping system, the need for machining will be minimized, resulting in reduced manufacturing costs, minimized material waste through scrap generation, improved material properties, increased process efficiency, reduced product design time, and reduced environmental contamination. The results of this work will also further the scientific understanding of nanostructured materials and net-shape forming techniques. Furthermore, collaborative activities with industry and national laboratories will be strengthened, and educational programs, including those for underrepresented minorities, will be enhanced.