Laser additive manufacturing of Inconel 718 at increased deposition rates

Abstract

Inconel 718 (IN718) is a nickel-based superalloy designed to display exceptionally high yield, tensile and creep-rupture properties at temperatures up to approx. 700 °C. For aerospace applications, it is the most widely used superalloy. The additive manufacturing process, laser-based direct energy deposition (DED) with powdery filler material can be used to repair, geometrically modify or manufacture components made of IN718. However, despite the devious advantages, its typical deposition rate of <0.5 kg/h is significantly lower than that of other DED processes such as metal inert gas (MIG) of wire + arc additive manufacturing (WAAM) – at about 10 kg/h – and electron beam additive manufacturing (EBAM®) with wire - at approx. 12 kg/h. Here, using IN718 as additive material, we targeted to increase the deposition rate of laser-based DED by a factor of more than ten and achieved a deposition rate of about 6 kg/h. For this purpose, we first developed a suitable process management strategy in combination with adapted system technology. Then, we built up samples with developed process parameters, from which tensile specimens for mechanical property tests were manufactured. Thereafter, the macro- and microstructures of the as-deposited material were analyzed. Based on the results, we applied a post heat treatment for modifying the microstructure and improving the mechanical properties. We demonstrated finally, the aerospace material specifications for the static mechanical properties can be achieved. This work shows a great potential of laser-based DED with increased deposition rate.