Effects of solution treatment on the microstructural evolution and tensile properties of GH 3230 superalloy manufactured by laser melting deposition

GH 3230 is a solution strengthening nickel-based superalloy, which is widely used to fabricate hot components involving service temperatures nearly or above 1100 °C. In this study, GH 3230 samples were fabricated by laser melting deposition (LMD) and the effects of solution treatment temperature ranging from 1200 °C to 1320 °C on the microstructure and tensile properties were investigated. Meanwhile, a comparison of the microstructure and properties of the different additive manufactured specimens and forgings were also made. The microstructure and phase evolution of the samples were examined with optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that the morphology of grain boundary carbides altered from chain-like to semi-chain short rod by the solution treatment, and the phase composition changed from a large amount of Cr23C6 phases and a small amount of Ni2W4C phases to a massive number of Ni2W4C phases. It was found that almost no change occurred with regard to the carbide content and the carbide size varied from 1.09 μm to 0.85 μm with the solution treatment temperature ranging from 1200 °C to 1260 °C. However, when the solution treatment temperature was further increased to 1320 °C, the content of carbides decreased dramatically from 4.35 vol% to 0.5 vol%, and the size of carbides decreased from 0.85 μm to 0.80 μm. In general, the solution treatment improved not only the ultimate tensile strength (UTS) but also the elongation (EL) of LMDed samples. The ultimate tensile strength could be increased from 1000 MPa (as-LMDed) to 1062.7 MPa (LMD + 1260 °C), and the elongation was enhanced from 16.7% to 24.3%.