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 similar to 1400 MPa and elongation of similar to 12 pct. Introducing an extra amount of Al into the IN718 alloy has also improved thermal stability, in which testing is conducted at 680 degrees C and held for 100hours. Meanwhile, it is noted that by a new heat treatment approach, the Al-doped IN718 alloy achieves the best fracture strength at similar to 1600 MPa and elongation at similar to 10 pct. The implications of the study have been addressed.