Cryogenic Wear of Novel High-Entropy Alloys

摩擦和磨损是导致结构合金能量损失、效率低下和失效的主要原因，对磨损机理的科学理解对于设计用于能源、制造和基础设施应用的高性能材料至关重要。最近发现了一种新的被称为高熵合金的合金，它既具有高强度，又具有非常高的耐磨性。该奖项支持研究，以确定两种新型高熵合金成分的高耐磨性的基本机制。从这项工作中获得的新知识有可能使高性能材料的设计能够在极端的使用环境中承受较大的力，包括在低温下的摩擦和磨损。参与研究活动的学生将在本科生和研究生阶段获得宝贵的教育经验。本研究项目的目的是检验这样的假设：高熵合金CoCrFeMnNi和碳掺杂Fe40.4Ni11.3Mn34.8Al7.5Cr6在77K时比不锈钢具有更好的耐磨性，这两种合金的接触表面在室温或77K的干滑动磨损中都能抵抗相变，磨损表面不会表现出铁磁性，而奥氏体不锈钢AISI 316将表现出这两个问题。在77K和293K下，在不同的滑动速度和不同的环境下，对这两种合金进行了干滑动销盘磨损试验，并与316不锈钢的磨损行为进行了比较。将确定显微组织、变形过程(包括材料转移)、相变、摩擦和磨损行为之间的关系。磨损前和磨损后样品的微观结构特征将包括透射电子显微镜、X射线色散光谱、计算机辅助轮廓术、X射线衍射、纳米压痕、横截面扫描电子显微镜、原子探针断层扫描和X射线光电子能谱。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Friction and wear are a leading cause of energy loss, inefficiency, and failure in structural alloys, and a scientific understanding of the mechanisms of wear is critical to the design of high performance materials for energy, manufacturing, and infrastructure applications. A new class of alloys known as High Entropy Alloys has recently been found to possess both high strength and the potential for very high wear resistance. This award supports research to determine the fundamental mechanisms of this high wear resistance in two novel High Entropy Alloy compositions. The new knowledge to be gained from this work has the potential to enable the design of high performance materials able to withstand large forces in extreme service environments, including friction and wear at cryogenic temperatures. Students engaged in the research activities will gain valuable educational experience at the undergraduate and graduate level.The aim of this research project is to examine the hypotheses that the high entropy alloys CoCrFeMnNi and carbon-doped Fe40.4Ni11.3Mn34.8Al7.5Cr6, because of their superior yield strengths compared to stainless steel, will show better wear resistance than stainless steel at 77 K, that that the contacting surfaces of the two alloys will be resistant to phase transformations during dry sliding wear at either room temperature or 77 K, and that the worn surfaces will not exhibit ferromagnetism, whereas austenitic stainless steel AISI 316 will exhibit both of these problems. Dry sliding pin-on-disk wear tests will be performed at both 77 K and 293 K at different sliding velocities and in different environments on these two alloys, and compared to the behavior of 316 stainless steel. The relationship between the microstructure, deformation processes (including material transfer), phase transformations, friction and wear behavior will be determined. Microstructural characterization of the pre- and post-wear specimens will include transmission electron microscopy, X-ray dispersive spectroscopy; computed-assisted profilometry; X-ray diffraction; nanoindentation; cross-sectional scanning electron microscopy, atom probe tomography; and X-ray photoelectron spectroscopy.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.