Development and additive manufacturing of oxide dispersion strengthened inconel 718: Thermochemical and experimental studies

Abstract

In this study, a new grade of Inconel 718 alloy (IN718) strengthened by nano-oxides has been designed and produced. The alloy composition of 0.3 wt% Y 2 O 3 – IN718 has been determined using CALPHAD-based thermochemical modeling approach. Designed ODS-IN718 alloy is produced by Selective Laser Melting (SLM) method with various power and velocity values to determine the best process parameters for this system. The SLM parameters are optimized for the production of ODS-IN718 alloy. To dissolve the non-equilibrium phases, which are detrimental to the mechanical properties, and maximize the number densities of nano-oxide and other strengthening phases of γ'/γ″, various heat treatment processes are applied based on the thermochemical calculations. The samples which are solutionized at 1050 °C for 1 h followed by aging at 650 °C for 5 h exhibit the best microstructural and mechanical properties. Tensile tests demonstrate that the strength and ductility of the solutionized and aged samples are much improved compared to the standard solutionized and double aged samples due to the fine and uniform microstructure, especially at elevated temperatures. It is observed that experimental results are consistent with the thermochemical modeling calculations. This clearly shows the promise of thermochemical calculations incorporating various databases for designing new alloy systems with nano-oxide strengthening. • A novel ODS-IN718 alloy is designed by thermochemical calculations and produced by selective laser melting (SLM) method. • A novel heat treatment is designed for maximizing number densities of nano-oxides and strengthening precipitates, γ'/γ″. • Y-Ti-O nano-oxides are detected in both as built and heat-treated states. • Experimental results are concordant with thermochemical calculations. • Alloy shows high microhardness, high density (>99%) and compatibility for production with SLM method.