Microstructure and comprehensive properties of Inconel 625 superalloy fabricated by oscillating laser directed energy deposition: Influence of heat treatment temperature

Oscillating laser directed energy deposition (OL-DED) is an advanced additive manufacturing technique for producing or repairing Inconel 625 components. However, the effect of post-heat treatment temperature on the comprehensive properties (mechanical, wear, corrosion) of OL-DED Inconel 625 remains unclear. In this study, Inconel 625 alloy was fabricated by infinity OL-DED and then heat treated at 800 °C, 1000 °C, and 1200 °C. Microstructures were characterized by SEM and XRD, while microhardness, wear resistance, tensile properties, and electrochemical corrosion behavior were systematically evaluated. At 800 °C, the deposition layer showed fully developed dendrites with high dislocation density and high hardness. Abrasive wear dominated, leading to larger wear volume and rate, but corrosion resistance was optimal (lowest corrosion current density, highest pitting potential). At 1000 °C, partial dendrite dissolution occurred, adhesive wear became dominant, and wear resistance improved. At 1200 °C, complete dendrite dissolution and recrystallization (89.8% recrystallized grains) were observed, characterized by a high fraction of high-angle grain boundaries and low dislocation density. This resulted in the highest elongation but reduced yield and ultimate tensile strengths. The fracture mechanism transformed from mixed ductile-brittle (800 °C) to fully ductile (1000 °C and 1200 °C). Corrosion resistance decreased with increasing heat treatment temperature due to reduced grain boundary density. These findings provide fundamental insights into heat-treatment-induced microstructure evolution in OL-DED Inconel 625 superalloy and offer guidance for tailoring mechanical, wear, and corrosion properties for high-performance applications in aerospace, energy, and marine engineering.