Effect of Thermal Aging on the Microstructure and Mechanical Properties of Inconel 625 Superalloy Fabricated by High-Speed Laser Metal Deposition

Compared to conventional laser metal deposition (LMD), high-speed laser metal deposition (HLMD) can significantly improve the efficiency with lower heat input to the existing deposit layer. However, non-equilibrium rapid solidification affects the high temperature stability of Inconel 625 superalloy, due to the high solidification rate under the high scanning speed in HLMD process. Therefore, appropriate post-processing techniques are required to control the properties of the materials, yet little research has been reported on the thermal aging treatment. In this work, the microstructural evolutions and room-temperature tension properties occurring upon thermal aging of Inconel 625 superalloy fabricated by HLMD were studied in the 500 °C to 900 °C temperature range for durations up to ~ 360 hours. When the temperature is below 700 °C, the microstructure is not obviously different from the as deposited. With the increase of aging temperature, however, the dendrite morphology gradually disappeared and the MC carbide formed at the end of solidification will undergo MC → M23C6/M6C transition. The δ phase precipitation temperature range of Inconel 625 superalloy under HLMD process is narrower than that under wrought process. The mechanical properties of the Inconel 625 superalloy under the HLMD processes have obvious anisotropy, but the tensile properties in the laser scanning direction are better than those in the perpendicular to laser scanning direction.