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Chrome moly钢（T91）和奥氏体不锈钢（AISI 316）之间创建功能梯度多层焊接过渡接头，展示对基于摩擦表面的增材制造建模和控制的全面理解。研究方法将是通过摩擦堆焊施加各种镍基合金层，在物理和冶金性能上产生平滑和渐进的过渡，以提高其蠕变寿命。 实验方案包括应力断裂和蠕变疲劳试验，以评估过渡接头的蠕变行为。原位有限元建模的研究方法涉及开发精细尺度晶体塑性和均匀化各向异性连续塑性模型，这将有助于获得使用基于摩擦表面的增材制造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部署T91和AISI 316焊接过渡接头，用于包括锅炉、核能和清洁能源概念在内的新兴项目中的结构。通过有限元模型开发，不仅可以制作T91/316接头，而且还可以开发基本的建模和制造基础设施，这些基础设施可以应用于难以加工的材料和/或熔焊产生不期望的金属间化合物形成的材料之间需要过渡接头的任何应用。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2）以更低的温室气体排放量发电 以及3）更大的量导致更好的生活质量。 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组件。该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开发，这将使学生接触到最先进的制造技术的进步。

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.