Microstructural charactristics of laser repaired Rene 142 turbine vane using Hastelloy W and C263 filler metals under high-temperature burner-rig test

Abstract

In this study, the repair of René-142 was performed using pulsed laser welding with two different filler metals: Hastelloy W (HW) and C263. HW was employed for the initial two weld passes, followed by five passes with C263. Following the repair process, the specimens were exposed to the burner-rig test at 900 °C for periods of 1 h and 200 h. The results revealed that, before the burner-rig test, the base metal exhibited a γ-phase matrix containing coarse, cuboidal γ′ precipitates, along with tantalum and tungsten carbide particles. A 1-h burner-rig test did not significantly alter the microstructure of the base metal. However, after 200 h, γ′′ precipitates replaced the γ′ precipitates, leading to a hardness reduction from 360 to 310 Vickers. Both HW and C263 initially exhibited a single γ phase. The 1-h burner-rig test led to the formation of grain boundary and intragranular Ni₂Mo and Ni₃Mo precipitates in the HW, increasing the hardness value from 360 to 420 Vickers. In contrast, C263 maintained microstructural stability after 1-h burner-rig test, decreasing the hardness value from 350 to 290 Vickers. Following 200-h burner-rig test, the microstructure of HW revealed a higher density of coarser NiMo precipitates, contributing to a hardness increase up to 511 Vickers. Additionally, coarse NiMo precipitates formed in the dilution zones of both C263 and HW. Nonetheless, C263 retained its single-phase structure, and its hardness decreased to 260 Vickers compared to the 1-h burner-rig test due to increased grain growth.