Design and Fabrication of Graded Materials with the Laser Engineered Net Shaping Process

本研究的目的是开发设计和制造渐变过渡接头，以避免在不同的焊缝失效的方法。 渐变过渡接头将包括成分和合成性能的逐渐和受控变化。这将大大减少或消除目前由成分和性能的急剧变化引起的异种焊接故障。首先使用结构优化程序来确定性能的最佳等级。这些信息将被用来制造各种渐变过渡接头使用微观结构建模和激光工程净成形（透镜）过程。这些接头的性能将使用各种技术相对于行业标准接头进行评估，包括光/电子显微镜、显微硬度测试、高温拉伸测试和蠕变断裂分析。然后，最佳级配接头将与传统接头一起沿着安装到工业合作伙伴的发电厂中，进行现场测试。随着对材料在应力、温度和腐蚀环境条件下的性能要求越来越高，预计对异种材料连接的需求将增加。梯度材料为连接不同材料提供了巨大的潜力，但设计这些接头以提高性能的方法还没有。此外，异种焊接失效目前带来显著的经济影响。例如，单个异种焊接故障可能使电力公司在停机时间和收入损失方面花费高达850，000美元/天。如果成功的话，这项研究的结果将导致开发用于优化可用于各种应用的梯度材料的设计，制造和性能的方法。结果也将导致在透镜处理过程中的处理，结构和性能之间的复杂关系的更好的理解。最后，在发电应用中直接实施异种材料连接技术将通过消除异种焊接故障来节省大量成本。

The objective of this research is to develop methods for designing and fabricating graded transition joints for avoiding failures in dissimilar welds. The graded transition joints will consist of gradual and controlled changes in composition and resultant properties. This will significantly reduce or eliminate failures in dissimilar welds that are currently caused by very sharp changes in composition and properties. The optimal gradation in properties will first be determined using structural optimization routines. This information will then be utilized to fabricate various graded transition joints using microstructural modeling and the Laser Engineered Net Shaping (LENS) process. The performance of these joints will be evaluated relative to the industry standard joints using a variety of techniques, including light/electron microscopy, microhardness testing, high temperature tensile testing, and creep-rupture analysis. Optimal graded joints will then be installed into the power plants of the industrial partner along with conventional joints for side-by-side field testing.The need to join dissimilar materials is expected to increase as more demand is placed on the performance of materials under conditions of increasing stress, temperature, and corrosive environment. Graded materials offer significant potential for joining dissimilar materials, but methods for designing these joints for improved performance are not yet available. In addition, dissimilar weld failures currently carry significant economic impact. For example, a single dissimilar weld failure can cost an electric power company up to $850,000/day in down time and lost revenue. If successful, the results of this research will lead to development of methods for optimizing the design, fabrication, and performance of graded materials that can be used in a variety of applications. The results will also lead to an improved understanding of the complex relationships between processing, structure, and properties in LENS processing. Lastly, the direct implementation of the technology for joining dissimilar materials in power generation applications will provide significant cost savings by eliminating dissimilar weld failures.