Laves phase tuning for enhancing high temperature mechanical property improvement in laser directed energy deposited Inconel 718

Improvement in high temperature material properties of aerospace alloys is critical to extend the performances of aeroengines. Apart from new alloy development, there is also great potential in optimizing the microstructure of laser directed energy deposited (Laser-DEDed) parts. This work reports a novel method of handling the undesirable and large-sized Laves phase particles in Laser-DEDed alloys. Experimental results demonstrate improvement in high temperature mechanical properties of IN718, by fully leveraging on the fast dissolution behaviors of the Laves phase in Laser-DEDed microstructure. The obtained Laser-DEDed IN718 contains about 1.55 vol % Laves phase with the dimension of 0.4-0.6 mm and aspect ratio of approximately 1.4. In particular, the high-temperature stress rupture (HTSR) performance of Laser-DEDed IN718 samples tested at 650 °C and 725 MPa (~130 h) exhibit a ~148% improvement in HRST life compared with the forged material (~51 h). It has been ascertained that the small and granular Laves phases have positive effects on the high-temperature mechanical properties of IN718. They can induce dynamic recrystallization to lower localized stress concentration and enhance high temperature performance.