RII Track-4: NSF: Development, Characterization and Performance Evaluation of Surface Engineered Additively Manufactured Parts for Nuclear Reactors

金属增材制造（AM）自发明以来得到了显著发展。在这个项目中，基于激光的定向能量沉积（DED）工艺将用于制造核反应堆应用的金属部件。顶部的几层将进一步设计使用超声波冲击喷丸处理，以提高其耐磨性。打印后，将使用中子衍射分析样品，以揭示沿制造样品的构建方向沿着在不同构建高度区域处的微观结构、残余应力和相分数的演变，从而将微观结构细节与工艺条件相关联。这些增材制造样本的摩擦和磨损行为将通过往复滑动和微动磨损测试进行。摩擦学是一门研究摩擦、磨损和润滑的科学，这使得它与表面工程密不可分。AM提供了独特的功能，可用于提高各种摩擦接触的可靠性。这个项目将探讨AM，表面工程和摩擦学之间的共生关系，特别是与核反应堆有关的滑动和微动接触问题。然而，从这项研究的主要发现将提供有价值的见解，以广泛的接触在关键应用，如生物医学，汽车和航空航天sectors.This研究基础设施改善轨道-4 EPSCoR研究员（RII轨道-4）项目将提供奖学金的助理教授和培训的研究生在北达科他州（UND）的大学。摩擦学是研究摩擦、磨损和润滑的科学，是一个复杂的、高度交叉的领域。有必要了解AM部件与传统制造部件的摩擦和磨损机制的差异，并深入了解材料特性，以实现适当的商业化。表面工程与材料科学有关，因为它涉及固体物质的表面。增材制造、表面工程和摩擦学具有相互依存的关系。我们的研究目标是利用这一观点开发下一代核反应堆部件，在不同温度下遇到摩擦和磨损时具有更高的可靠性和可定制性。我们将利用定制的基于激光的定向能量沉积（DED）技术，配备超声冲击强化（UIP）能力，制造由Nitronic 60不锈钢制成的功能梯度金属部件。Nitronic 60是一种廉价的奥氏体不锈钢，由于其耐磨损性能而广泛用于核领域。这种材料能呈现出耐高温磨损和耐腐蚀的特性，广泛应用于阀座、衬套、滚子轴承、套圈等。我们认为，UIP处理过程中优化的工艺参数可以导致在Nitronic 60的沉积近表面层中应变诱导FCC到HCP马氏体相变（SIM），并且增强的材料状态，例如具有细化晶粒的残余应力，可以导致改善的摩擦学行为。通过对相组成的理解，揭示了沉积Nitronic 60的工艺-微观结构-性能，通过中子衍射，残余应力沿着构建高度的演变，并与往复摩擦和磨损试验以及网格到该奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的支持影响审查标准。

Metal additive manufacturing (AM) has developed significantly since its invention. In this project, a laser-based directed energy deposition (DED) process will be utilized to fabricate metallic parts for nuclear reactor application. The top few layers will be further engineered using an ultrasonic impact peening treatment to enhance its wear resistance. Post printing, the samples will be analyzed using neutron diffraction to reveal the evolution of microstructure, residual stress, and phase fractions at different build height regions along the build direction of fabricated samples to correlate the microstructural details with process conditions. Friction and wear behavior of these additively manufactured samples will be conducted via both reciprocating sliding and fretting wear testing. Tribology is the science of friction, wear, and lubrication, making it inherently inseparable from surface engineering. AM offers unique capabilities that can be leveraged to enhance the reliability of various tribological contacts. This project will explore the symbiotic relationship between AM, surface engineering, and tribology with respect to sliding and fretting contact problems specifically connected to nuclear reactors. However, the major findings from this research will provide valuable insights to wide varieties of contacts in critical applications, such as biomedical, automotive, and aerospace sectors.This Research Infrastructure Improvement Track-4 EPSCoR Research Fellows (RII Track-4) project would provide a fellowship to an Assistant professor and training for a graduate student at the University of North Dakota (UND). Tribology, a complex and highly interdisciplinary field, is the science of friction, wear, and lubrication. It is necessary to understand the differences in an AM part’s friction and wear mechanism compared to traditionally fabricated parts and in-depth material characterizations for proper commercialization. Surface engineering is connected to materials science since it pertains to the surface of solid matter. Additive manufacturing, surface engineering, and tribology have an interdependent relationship. Our research goal is to leverage this perspective to develop next-generation nuclear reactor components with enhanced reliability and customizability when encountering friction and wear at different temperatures. We will fabricate functionally graded metallic components made of Nitronic 60 stainless steel by leveraging customized laser-based directed energy deposition (DED) technique equipped with an ultrasonic impact peening (UIP) capability. Nitronic 60 is an inexpensive austenitic stainless steel widely used in the nuclear sector due to its galling-resistance properties. This material can present high-temperature wear and corrosion resistance, and widely used in valve seats, bushings, roller bearings, and rings. We believe that optimized process parameters during UIP treatment can result in a strain-induced FCC to HCP martensitic phase transformation (SIM) in the deposited near-surface layers of Nitronic 60, and enhanced materials states, such as residual stress with refined grains, can result in improved tribological behavior. Process-microstructure-property of deposited Nitronic 60 will be revealed by understanding phase fractions, residual stress evolution along build height through neutron diffraction and correlated that with reciprocating friction and wear testing as well as grid-to-rod fretting characteristics of fabricated samples.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.