Physics and Statistics Based Selection of SLM and EBM Process Parameters to Mitigate Defects and to Control Deposit Microstructure

The ability to assign a level of confidence for build quality is fundamental to the deployment of powder bed technology. Accordingly, the research objective of this work is to use probability theory as a glue to combine the physics-based models used for the selection of processing parameters together in order to produce quality deposits using the following approach: (1) Use probability theory as the glue to combine physics-based models for melt-pool thermal-fluid behavior and track cross-section formation in order to determine the deposition parameters; (2) Enhance the physics-based model to predict vaporization and expulsion of the additive material, melt pool buckling, transport of gas bubbles, determination of hatch distance, inter-track and inter-layer wetting; (3) Perform probabilistic assessment for the performance of the deposition parameters for their ability to mitigate defects, attain consistency of size for the fused tracks, flatness of the top layer, and the material microstructure; (4) Use the solidification parameters and thermal cycling during deposition to predict the precipitation reactions; (5) Perform deposition experiments to demonstrate the ability to engineer the deposition parameters. This work would result in reduction of effort for the development of process parameters and part qualification for specialty materials of interest to NASA.

The NASA application is to enable physics-based selection of SLM and EBM process parameters, while taking into account the statistics of substrate roughness, scanning direction and track formation. It is designed to reduce the effort needed to meet certification requirements for NASA parts. This application is needed because the current use of SLM and EBM uses process parameters that are developed on the basis of experimental trial and error; and these parameters are available for only a few alloys. This work is expected to reduce effort for the selection of process parameter for new alloys by up to a factor of two to four.

Physics-based selection of SLM and EBM process parameters to mitigate defects and to control microstructure for materials utilized in the land or sea-based gas-turbine engines, for life-extension of aging systems, etc.

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