Microstructural evolution of laser repair welded rene 142 superalloy with IN625/C263 welding materials

Abstract In this study, the repair of directionally solidified turbine vanes made of René-142 superalloy was conducted using pulsed laser welding with two different filler metals, IN625 and C263. The first two weld passes were deposited using IN625, while the final five passes were completed with C263. Subsequently, the repaired samples were subjected to a burner-rig test under engine operating temperature conditions (900 °C) for durations of 1 h and 200 h. The results indicate that the repaired samples were defect-free, and no cracks were observed in the material following the burner-rig test. Prior to the burner-rig test, the base metal exhibited gamma ( γ ), gamma prime ( γ ′), and tantalum- and tungsten-based carbides. However, after 200 h of exposure, the γ ′ phase dissolved, and a Ni 3 Ta phase formed in the base metal. The microhardness of base metal remained unchanged after the 1 h test but decreased from 365 Vickers to 340 Vickers after 200 h. Microstructural observations and x-ray diffraction analysis revealed that both filler metals were initially composed of a single-phase γ structure before the burner-rig test. After the test, δ -phase precipitates formed in the IN625, and these precipitates coarsened with increasing exposure time. Consequently, the microhardness of the IN625 increased from approximately 280 Vickers to 320 Vickers after 1 h and to 368 vickers after 200 h. In contrast, the C263 developed NiMo precipitates after the burner-rig test, leading to a reduction in microhardness from 348 Vickers to 292 Vickers after 1 h and to 246 vickers after 200 h.