Investigation of Heat Treatment Effects on Hybrid Manufacturing of Stainless Steel 316L Components Using Directed Energy Deposition: Microstructural and Tensile Behavior Analysis

This research investigates the effects of heat treatments on the tensile properties and microstructure of hot-rolled SS316L steel repaired using the Directed Energy Deposition (DED) process with SS316L powder. The applied heat treatments were solution annealing at 650 °C for 6 hours (HT1) and hot isostatic pressing at 1100 °C for 4 hours followed by solution treatment at 1050 °C for 1 hour (HT2). The study compared as-built (ABS), HT1, and HT2 samples to understand mechanical properties and fracture behavior changes. The ABS sample showed high residual stresses, small grains, and the highest strength but lowest ductility. HT1 improved ductility and grain uniformity, while HT2 achieved the highest ductility and extensive grain growth. Fracture features transitioned from mixed brittle–ductile in ABS to predominantly ductile in HT2. XRD analysis showed a shift from dominant austenite peaks in ABS to sharper austenite peaks and minor carbide peaks in HT2. These heat treatments significantly enhanced the microstructure and mechanical properties of SS316L, highlighting the importance of tailored heat treatments for optimizing DED-repaired materials in engineering applications.