Electrochemical Study of Selective Laser Melted Inconel 718 Alloy Subjected to Varying Aging Durations

Abstract

In this study, heat treatment with varying aging durations is applied on specimens produced by selective laser melting of pre-alloyed powder of Inconel 718 alloy (IN718) to evaluate the impact of aging duration on the microstructure and corrosion resistance. A two-stage aging procedure was adopted after homogenizing the samples at 1000°C for 1 h. The aging was initially done at 740°C for 8 h then cooled to 620°C and kept for 8 h, 15 h, 25 h, and 40 h in the second stage before finally being normalized under ambient conditions. The results revealed that corrosion resistance improved significantly with longer aging durations, with the 40-h aged sample exhibiting the highest resistance. The enhanced corrosion resistance is attributed to the precipitation of γ′ and γ″ phases. Pitting corrosion resistance increased with aging duration up to 15 h in the second stage, then slightly decreased because of overaging. Similarly, hardness declined slightly beyond 25 h of aging because of the transformation of γ′ and γ″ phases into the δ phase. This study emphasizes the need for precise control of aging durations to optimize corrosion resistance and mechanical properties.