In the direct energy deposition (DED) process, the highly energetic laser, rapid melting, and solidification processes lead to complex heat transfer and flow phenomena. A three-dimensional finite element model (FEM) is established to study the effect of process parameters on the melt pool and solidification quality during the DED process. The heat transfer, fluid flow, and solidification in the DED process of the GH3536 superalloy are studied. By investigating the effects of laser power, scanning speed, and feed rate on the morphology of melt pool and interlayer fusion, the appropriate input parameters for GH3536 are obtained. Temperature gradient and solidification rate obtained in transient thermal distribution are applied to predict the quality and morphology of the solidified structure at the cut-off point. Results show that high laser power and low scanning speed or feed rate will enlarge the melt pool. Well-solidified microstructure frequently appears in the middle of the parameter set; focusing on the enlargement of the melt pool is not the best strategy. The correlation between feed rate and laser power is not obvious. The minimum threshold for scanning speed is found at a given feed rate. When the scanning rate is below the threshold, abnormal morphology of the melt pool and irregular solidification structures will occur. The laser power and scanning speed range suitable for the GH3536 superalloy are summarized, and the undesirable and possibly fluctuating parameters are marked. The middle part of the parameter set is recommended for the feed rate.

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