Restoring welded inconel 625 integrity: a comprehensive multi-technique analysis of optimized post-weld heat treatment

This study examines the impact of post-weld heat treatment (PWHT) on TIG-welded Inconel 625 alloy. Seven TIG welding passes under pure argon shielding gas were utilized to join 10 mm-thick plates prepared with V-groove edge machining. Welded plates were subsequently sectioned into ASTM E8/E8M-compliant dog bone and disc specimens for mechanical testing. The PWHT involved solution annealing at 1060 °C for 2 h followed by rapid quenching, controlled furnace cooling, and a sub-critical temperature soak at 600–800 °C. Mechanical properties were evaluated through tensile testing, pin-on-disc wear tests, and Vickers microhardness measurements. Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDX) analyses of the base and fusion zones revealed dissolution of detrimental Laves and δ phases, a homogenized γ-matrix structure, and restored elemental uniformity. However, previous studies have not clearly connected these microstructural changes to the corresponding mechanical and tribological behavior across different weld zones. Heat-treated samples exhibited consistent hardness, maintained tensile strength, improved ductility, and a significant reduction (15%) in friction coefficient. These enhancements confirm the suitability of optimized thermal cycles for restoring solid-solution strengthening and dimensional stability, making the alloy particularly suitable for demanding aerospace and power generation applications exposed to high temperatures and corrosive environments.