Reactive introduction of oxide nanoparticles in additively manufactured 718 Ni alloys with improved high temperature performance

Abstract

Alloy 718 has been intensively investigated for additive manufacturing. While previous studies on additively manufactured alloy 718 typically have metallic phases only, in this work, we show that oxide nanoparticles can be introduced into alloy 718 via a reactive sintering mechanism. The introduction of micron scale Cr 2 O 3 powder in alloy 718 powder led to the formation of a homogeneous distribution of Al and Ti rich oxide nanoparticles. This surprising finding arises from the chemical reaction between oxide powders and metal matrix containing Al and Ti. In comparison to the control alloy 718 without oxides, the presence of oxide nanoparticles dramatically alters the microstructure, leading to a relatively more equiaxed grain structure, while also reducing the residual stress. While the mechanical testing between the two material groups demonstrates comparable mechanical strength and tensile ductility at room temperature, the high-temperature (900 °C) mechanical properties of the oxide containing 718 samples were significantly improved over the control 718 samples. The apparent possibilities of using this reactive process to introduce oxide nanoparticles into metallic materials may have a general implication for the fabrication of oxide dispersion in various metal matrices via reactive additive manufacturing. • Production of nano oxide dispersion strengthened alloy 718 • Reactive formation of oxide nano particles creates a (Al,Ti) 2 O 3 chemistry • Reduction of residual stress via the oxide particles accommodating residual stress • Increased high-temperature mechanical properties up to 900 °C