Additive manufacturing of Hastelloy X: the effects of the process parameters on the state of the residual stress and material microstructure

减少温室气体排放的需求促使工程师们设计新的材料工艺，以实现性能的优化。这包括优化零部件几何结构，以高效地完成相同的任务。加法制造是少数几种允许工程师制造具有复杂几何形状的部件的制造方法之一。在这种方法中，部件的几何形状通常是在计算机中设计的，计算机将几何数据提供给硬件，从而逐层沉积材料。激光功率床融合(LPBF)是一种附加制造技术，它使用激光熔化在前一层上添加的一层金属粉末。它最近被用于制造燃气轮机的镍基部件。例如，Hastelloy-X是一种镍基高温合金，用于使用LPBF方法制造涡轮机部件。由于从液态金属到最终固体部件的温度差异很大，在LPBF添加剂制造过程中，部件中会产生热残余应力；这可能会显著影响最终产品的性能或其疲劳寿命。本项目将重点研究LPBF工艺参数对残余应力状态和材料微观结构的影响。西门子已经开发了预测最终产品中残余应力状态的数值模型，但它们需要验证数据。我们将使用基于实验室的X射线方法来测量Hastelloy-X组件的表面应力。内应力将使用中子和同步辐射X射线衍射仪进行测量。此外，还将研究显微组织随工艺参数的变化情况。这是为了了解将Hastelloys-X微结构与部件性能联系起来的潜在机制。西门子将利用这些信息进一步提高涡轮机部件的制造效率。

The demand for reducing greenhouse gases has led engineers to design new materials processes that would result in optimized performance. This includes optimizing component geometry to deliver the same task, but efficiently. Additive manufacturing is one of the few manufacturing methods that allows engineers to make components with complex geometries. In this method, the geometry of the component is normally designed in a computer which feeds the geometry data to a hardware that deposit materials layer upon layer.Laser power bed fusion (LPBF) is one of the additive manufacturing techniques that uses laser to melt a thin layer of metal powder that is added upon the previous layer. It is recently employed for manufacturing the nickel-based components of gas turbine. For example, Hastelloy-X is a nickel based superalloy that is used for manufacturing turbine components using LPBF method. Due to significant temperature variation from liquid metal to final solid component, thermal residual stresses develop in the component during LPBF additive manufacturing; this can significantly affect the performance of the final product or their fatigue life. This project will focus on characterizing the state of the residual stresses and materials microstructures as a function of LPBF process parameters. Numerical models have been developed at Siemens that predict the state of the residual stresses in the end-product, but they need validation data. We will use Lab-based X-ray methods to measure surface stresses in Hastelloy-X components. Internal stresses will be measured by the use of neutron and synchrotron X-ray diffraction. Further, the variation of microstructure as function of process parameters will be studied. This is to understand the underlying mechanism that relates Hastelloys-X microstructures to component performance. This information will be used by Siemens to further advance the efficient manufacturing of turbine components.