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In this paper, the microstructure and mechanical properties of SLM-GH3230 superalloy treated by different post treatments (single hot isostatic pressing and heat treatments after hot isostatic pressing) were studied. The micro-morphologies show that the grains along building direction after HIP + HT are mainly columnar grains, which is consistent to that after single HIP. The granular precipitates distribute intergranularly and intragranularly after HIP, but gradually re-dissolve into matrix with the increase of the temperature of the post HT processes. XRD and EDS analyses results indicate that the matrix mainly consists of austenitic γ phase and the granular precipitates are mainly M6C carbides enriched in W element. The average grain size decreases after HT compared to that after HIP, and the crystallographic orientation of grains tends to be more uniform. The Vickers hardness decreases after HIP and HIP + HT processes within a certain degree. According to tensile test results, the sample shows a better combination of strength and plastic performance under HIP+1250 °C/30 min processing, which can also be verified by the characteristic of the fracture morphology with more tearing dimples.