Material and process design for additive manufacturing of hard metals

耐磨材料的设计是一个可以提供显著工业效益的领域，从建筑、机械加工和制造部门的应用。尽管如此，耐磨材料的创新，特别是与金属基材料相关的创新，受到加工和原型制造过程中遇到的限制，因此，很少有新材料能够与碳化钨(WC)基部件竞争。然而，添加剂制造(AM)方法的快速增长和发展为新的耐磨材料及其制造工艺的整体设计提供了途径。使用AM，可以将加工修改为在非平衡状态下进行，并且这些方法可以用于将硬化相的形成定制到后处理循环的较后阶段，从而允许改善材料的加工性。因此，本项目的目的是探索使用AM-BASE方法进行耐磨应用的材料设计和加工的途径。该项目将侧重于初步评估三类材料的潜力和加工性：高熵合金和高熵碳化物，以及高熵硬质合金设计和高硬度钢的可能性。材料设计工作将集中在高熵合金和可淬火钢上。高熵合金是冶金研究的一个领域，在过去的几年里呈指数级增长，但很少有研究评估高熵合金的耐磨性。在这项工作中，在进行进一步的AM加工和耐磨性测试之前，将对几种难熔金属高熵合金(HEA)的成分进行初步的硬度和加工性评估。此外，还将探讨使用AM后处理热处理诱导显著碳化物形成的可能性。已知几种HEA在高温下长时间暴露后会导致碳化物物种的析出。通过在有希望的系统中试验碳含量和AM工艺，可以显著改变碳化物形成的动力学，以在工业上可行的热处理时间内诱导碳化物的形成。此外，如果时间允许，已知存在几种基于难熔金属的高硬度高熵碳化物(HEC)，也可以评估HEC-HEA类型的硬质合金系统。

The design of materials resistant to wear is an area that could offer significant industrial benefits ranging from applications in the construction, machining and manufacturing sectors. Despite that, wear resistant material innovation, in particular related to metal-based materials, is limited by constraints encountered in processing and prototyping and hence, few novel materials have been able to compete with tungsten carbide (WC) based components. However, the rapid growth and development of additive manufacturing (AM) methods offers an avenue for the holistic design of both new wear resistant materials and their manufacturing process. Using AM, processing can be modified to occur at non-equilibrium states and these methods can be used to tailor the formation of hardening phases to a later stage in the post-processing cycles, hence allowing for improved material processability. It is therefore the aim of this project to investigate avenues for materials design and processing for wear resistant applications using AM-based methods. The project will focus on the evaluating the potential and processability of three classes of materials initially: high entropy alloys and high entropy carbides and the possibilities of high entropy cemented carbide design and high-hardness steels. Material design efforts will focus on high entropy alloys and hardenable steels. High entropy alloys have provided a domain of metallurgical research that has expanded exponentially over the last few years, yet few studies have evaluated high entropy alloys for wear resistance. In this work several compositions of refractory metal high entropy alloys (HEAs) will be initially evaluated for hardness and processability, before further AM processing and wear resistance tests can be carried out. In addition, the possibilities of inducing significant carbide formation using post-AM processing heat treatments will be explored. Several HEAs are known to result in the precipitation of carbide species following prolonged exposures at high temperatures. By experimenting with the C content as well as AM processing within promising systems, the kinetics of carbide formation can be significantly altered to induce carbide formation with industrially viable heat treatment durations. Furthermore, and if time permits, several species of high-hardness high entropy carbides (HEC) based on refractory metals are known to exist and HEC-HEA type cemented carbide systems may also be evaluated.