Refurbishment of first stage turbine vane made of directionally solidified René-142 superalloy with laser welding process

In this study, pulsed laser welding was utilized to repair directionally solidified turbine vanes made of René-142 with two distinct filler materials, Hastelloy X (HX) and C263. During the repair process, two initial weld passes were applied using HX, followed by five subsequent passes with C263. The repaired samples were then subjected to a burner-rig test under engine-operating temperature conditions (900 °C) for durations of 1 and 200 h. The microstructural transformations were analyzed using optical microscopy and scanning electron microscopy. Before the burner-rig test, the base metal microstructure consisted of gamma (γ), secondary γ′ precipitates, and tungsten and tantalum carbides. The 1 h burner-rig test had no significant effect on the base metal microstructure. However, after the 200 h burner-rig test, γ″ (Ni3Ta) precipitates replaced the original γ′ (Ni3Al) precipitates, leading to a decrease in base metal hardness from 360 to 300 Vickers. Microstructural analysis revealed that both HX and C263 filler metals initially consisted of a γ-phase structure before the burner-rig test. Following the burner-rig test, M6C-type carbides formed in the HX weld metal, resulting in an increase in the hardness value from 250 to 270 Vickers after 1 h and to 330 Vickers after 200 h. In contrast, in the C263 weld metal, MC-type carbides formed after the burner-rig test, leading to a decrease in the hardness value from 350 to 295 Vickers after 1 h and to 250 Vickers after 200 h.