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

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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.