Effects of Post-Heat Treatment and Carbide Precipitates on Strength-Ductility Balance of GH3536 Superalloy Prepared by Selective Laser Melting

The strength and ductility cannot achieve a good tradeoff for some superalloy (e.g. GH3536) prepared by selective laser melting (SLM), which seriously restricts their industrial applications. This work examined the effect of post-heat treatment (HT) on the microstructure and mechanical properties of GH3536 produced by SLM. In particular, the influence of carbide precipitate morphology and distribution on strength and ductility of the alloy after heat treatment was discussed. After aging at 650 °C (denoted as HT1), the Cr₂₃C₆ carbides were distributed in chains. The ductility increased by approximately 31%, while the strength slightly decreased. After aging at 745 °C (denoted as HT2), the Cr₂₃C₆ carbides were distributed in chains. However, the HT2 samples showed an increase in ductility of ~ 58% and no reduction in strength. As the dislocation density of HT2 sample was higher than that of the HT1 sample, the chain carbides could be pinned to the grain boundaries, consequently improving the ductility but no loss in strength as compared with the as-deposited samples. When the aging temperature was increased to 900 °C (denoted as HT3), the carbides were distributed in a discontinuous granular form. As a result, the HT3 samples presented the lowest dislocation density which reduced the strength.