Collaborative Research: Modeling and Characterization of Transition Joints Made by Friction Surfacing Based Additive Manufacturing (FSAM)

这项合作研究的研究目标是通过在铬钼钢（T91）和奥氏体不锈钢（AISI316）之间创建一个功能分级的多层焊接过渡接头，展示对基于摩擦表面的增材制造的建模和控制的全面理解。研究方法将是采用摩擦堆焊的方法，使各种镍基合金层在物理和冶金性能上产生平滑和逐渐的转变，以提高其蠕变寿命。试验程序包括应力断裂和蠕变疲劳试验，以评估过渡节点的蠕变行为。原位有限元建模的研究方法包括建立细尺度晶体塑性和均质各向异性连续塑性模型，这将有助于获得摩擦表面增材制造部件的优化工艺参数。如果成功，这项研究将有助于加速T91和AISI316焊接过渡接头在新兴项目结构中的部署，包括锅炉、核能和清洁能源概念。通过有限元模型的开发，不仅可以制造T91/316接头，而且可以开发基本的建模和制造基础设施，可以应用于任何需要在难以加工的材料和/或熔焊产生不良金属间形成的材料之间进行过渡接头的应用。这项研究的成功完成将使高温发电厂能够1)以更低的成本发电2)减少温室气体排放3)大量发电，从而提高生活质量。研究结果还将有助于在许多其他工程行业中制造性能更好和优化的部件。本提案的教育目标将侧重于培养博士后研究人员、研究生和本科生。高级表面技术课程将被开发，这将使学生接触到最先进的制造技术。

The research objective of this collaborative study is to demonstrate a comprehensive understanding of modeling and control of Friction Surfacing-based Additive Manufacturing by creating a functionally graded, multi-layered weld transition joint between chrome moly steel (T91) and austenitic stainless steel (AISI316). The research approach will be to apply various nickel based alloy layers by friction surfacing, creating a smooth and gradual transition in physical and metallurgical properties to improve their creep life. The experimental program involves stress rupture and creep-fatigue tests to assess the creep behavior of the transition joints. The research approach for in-situ finite element modeling involves development of fine-scale crystal plasticity and homogenized anisotropic continuum plasticity models, which will help in obtaining the optimized process parameters for the fabrication of components using Friction Surfacing-based Additive Manufacturing. If successful, this research will aid the accelerated deployment of T91 and AISI316 weld transitional joints for structures in emerging initiatives including boiler, nuclear and clean energy concepts. Through the finite element model development, not only can T91/316 joints be made, but a basic modeling and manufacturing infrastructure will be developed that can be applied to any application where transitional joints are needed between hard-to-process materials and/or materials where fusion welding produces undesirable intermetallic formation. The successful completion of this research will enable higher-temperature power plants to generate power 1) at lower cost 2) with lower greenhouse gas emissions and 3) in larger quantities resulting in a better quality of life. The results will also help make it possible to manufacture better performing and optimized components in a host of other engineering industries. The educational objectives of the proposal will focus on training of post-doctoral researchers, graduate and undergraduate students. Advanced Surface Technology course will be developed which will expose the students to the state-of-the-art advances in manufacturing technologies.