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

金属添加剂制造自问世以来得到了长足的发展。在这个项目中，基于激光的定向能量沉积(DED)工艺将被用于制造核反应堆应用的金属部件。最上面的几层将进一步采用超声波冲击喷丸处理，以增强其耐磨性。打印后，将使用中子衍射对样品进行分析，以揭示沿制备样品的构建方向不同构建高度区域的微观结构、残余应力和相组成的演变，从而将微观结构细节与工艺条件相关联。将通过往复滑动和微动磨损试验来测试这些添加制造的样品的摩擦磨损行为。摩擦学是一门研究摩擦、磨损和润滑的科学，因此它本质上与表面工程密不可分。AM提供独特的功能，可用于提高各种摩擦学接触的可靠性。这个项目将探索AM、表面工程和摩擦学之间在滑动和微动接触问题方面的共生关系，这些问题特别与核反应堆有关。然而，这项研究的主要发现将为关键应用领域的各种联系人提供有价值的见解。这项研究基础设施改善Track-4 EPSCoR研究人员(RII Track-4)项目将为北达科他州大学(UND)的一名助理教授提供奖学金，并为一名研究生提供培训。摩擦学是一个复杂的、高度交叉的领域，是研究摩擦、磨损和润滑的科学。有必要了解AM部件与传统制造部件的摩擦磨损机制的差异，并深入了解材料特性，以便实现适当的商业化。表面工程与材料科学有关，因为它与固体物质的表面有关。添加剂制造、表面工程和摩擦学之间存在相互依存的关系。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定制化能力。我们将利用配备超声冲击喷丸(UIP)能力的定制激光定向能沉积(DED)技术，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，由于其抗磨损性能而广泛应用于核工业。这种材料具有耐高温磨损和耐腐蚀性，广泛用于阀座、衬套、滚子轴承和套圈。我们认为，在UIP处理过程中，优化的工艺参数可以导致Nitronic 60沉积的近表层发生应变诱导的面心立方向六方相变(SIM)，并改善材料状态，如细化晶粒的残余应力，可以改善摩擦学行为。Nitronic 60沉积的工艺-微结构-性能将通过了解相组成、通过中子衍射沿构建高度的残余应力演变以及与往复摩擦和磨损测试以及制造样品的栅极到杆的微动特性相关联来揭示。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。

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.