Abstract
An integrated simulation framework consisting of the 3D finite element method and 3D cellular automaton method is presented for simulating the multi-track and multi-layer selective laser melting (SLM) process. The framework takes account of all the major multi-physics phenomena in the SLM process, including the initial grain structure, the growth kinetics, the laser scanning strategy, the laser–powder and laser–matter interactions, the melt flow, and the powder-to-liquid-to-solid transformations. The feasibility of the proposed framework is demonstrated by simulating the evolution of the epitaxy grain structure of Inconel 718 (IN718) during a 15-layer SLM process performed using a bi-directional 67° rotation scanning strategy and various SLM process parameters. The simulation results are found to be in good agreement with the experimental observations obtained in the present study and in the literature. In particular, a strong (001) texture is observed in the final component, which indicates that the grains with a preferred <001> orientation win the competitive epitaxy grain growth process. In addition, the size and shape of the IN718 grains are governed primarily by the cooling rate, where the cooling rate is determined in turn by the SLM parameters and the build height. Overall, the results show that the proposed framework provides an accurate approach for predicting the final microstructures of SLM components, and therefore, it can play an important role in optimizing the SLM processing parameters in such a way as to produce components with the desired mechanical properties.
Highlights
Accepted: 29 November 2021Selective laser melting (SLM) is a key technology for the fabrication of many components in the aerospace, automotive, and healthcare fields nowadays
The feasibility of the proposed model is demonstrated by simulating the microstructural evolution of Inconel 718 (IN718) alloy during a 15-layer multi-track SLM process performed with various laser powers, scanning speeds, and hatch densities
Since the main growth mode in the SLM processing of Ni super alloys such as IN718 is epitaxy growth [27,28,29], the simulations commenced by depositing an initial substrate consisting of 15 layers using a laser power, scanning speed, and hatch distance of 150 W, 800 mm/s, and 100 μm, respectively, and a bi-directional 67° rotation scanning strategy
Summary
Selective laser melting (SLM) is a key technology for the fabrication of many components in the aerospace, automotive, and healthcare fields nowadays. The feasibility of the proposed model is demonstrated by simulating the microstructural evolution of IN718 alloy during a 15-layer multi-track SLM process performed with various laser powers, scanning speeds, and hatch densities. Since the main growth mode in the SLM processing of Ni super alloys such as IN718 is epitaxy growth [27,28,29], the simulations commenced by depositing an initial substrate consisting of 15 layers using a laser power, scanning speed, and hatch distance of 150 W, 800 mm/s, and 100 μm, respectively, and a bi-directional 67° rotation scanning strategy. The simulations considered an epitaxy growth mode in which the partially re-melted grains in the previous layer (or the initial substrate in the case of the first layer) underwent a process of competitive epitaxy growth in accordance with their preferred growth directions. All of the layers in the built component remained computationally active until the end of the simulation process
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