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In order to achieve the microstructure homogeneity at a lower temperature and improve the mechanical properties, a novel post heat treatment was introduced to Inconel 718 fabricated by laser direct energy deposition (LDED), by means of δaging treatment + solution treatment. The microstructure analysis shows that the fully precipitation of δphase in LDED Inconel 718 superalloy can “cut” the long strip Laves phase into small pieces. According with the δphase solution treated at 1020 °C for 30 min, only tiny particle Laves phase was remained. The equilibrium volume fraction of Laves phase after δphase solution treatment is about 1%, which is much lower than that of the as-deposited sample or the sample only solution treated at 1020 °C. Due to the solution strengthening and precipitation of γ″ phase during aging treatment, the tensile strength of δaging + δsolution + double aging treated samples was 10.27% higher than that of directed solution + double aging treated samples, as well as a 31.38% and 52.71% increases in elongation and the reduction of area during tensile tests.

Laser cladding repair technology is valued for its ability to repair of damaged parts with high performance. However, there are so many parameters affect the repair quality that it takes a lot of work to determine the optimal parameters. In this article, a variety of parameters were combined as dimensionless heat input (Q*), and the effect of Q* on the microstructure and mechanical properties of 300M steel repaired samples were studied. Results showed that with the increase of Q*, microstructure of heat affected zone transformed from tempered martensite to tempered martensite and low bainite. The microstructure of the repaired zone transformed from untempered martensite to untempered martensite and a small amount of retained austenite. With increasing of Q*, residence time above the austenitizing temperature was extended, and more uniform microstructure were obtained in the repaired zone. What’s more, at Q* = 5.1, the repair efficiency increases twice than Q* = 1. The tensile strength of the repaired samples reached 1017.6 MPa and the elongation reached 6.9 %, which were far lower than that of forged samples. The heat treatment was carried out on the repaired parts, which eliminated the microstructure difference due to different Q*. Compared with the repaired samples without heat treatment, the tensile strength increased by 75 % to 1783.8 MPa and the elongation increased by 86 % to 10.4 %.