Mechanically Blended Al: Simple but Effective Approach to Improving Mechanical Property and Thermal Stability of Selective Laser-Melted Inconel 718

Inconel718 (IN718) superalloy is one of the most widely employed high-temperature materials. How to improve its working temperature limit is a challenging but rewarding task. In this study, we have proved that by simply mechanical blending pre-alloyed IN718 powder with elemental Al powder, one can successfully add extra Al to the IN718 alloy. The Al-added IN718 alloys developed by this study show homogenous distribution of Al in the as-printed microstructure produced by selective laser melting (SLM), and only a slight loss of the Al amount is detected due to SLM in situ alloying. Excellent relative density of > 99.5 pct has been achieved, and after the standard heat treatment, the IN718 + 0.5Al alloy shows good mechanical properties, achieving a fracture strength of ~ 1400 MPa and elongation of ~ 12 pct. Introducing an extra amount of Al into the IN718 alloy has also improved thermal stability, in which testing is conducted at 680 °C and held for 100 hours. Meanwhile, it is noted that by a new heat treatment approach, the Al-doped IN718 alloy achieves the best fracture strength at ~ 1600 MPa and elongation at ~ 10 pct. The implications of the study have been addressed.