Investigation of the As-Cast Microstructure, Stability, Wear and Corrosion Resistance of Alloy 625 + WC Nanocomposites Processed Through Suction Casting as Repair Materials for Ni-Based Superalloys

Abstract While maintenance, repair, and operations are crucial for improving the performance of gas turbine components, the properties of filler metal, such as Inconel alloys, may be insufficient in extremely harsh environments, necessitating the use of alternative materials need to be implemented. In this study, Alloy 625-based composites reinforced with varying WC (tungsten carbides) nanoparticles (1.25, 2.5, 3.75, or 5.0 wt pct) were fabricated via suction casting. The dendrites in both Alloy 625 and the WC-reinforced nanocomposites consisted of the γ matrix, and segregation of alloying elements in the interdendritic regions resulted in additional carbides and Laves phase precipitates were additionally observed. Synchrotron radiation experiments and microstructure investigations revealed that the partial dissolution of WC promoted the formation of Nb-rich MC and Mo, W-rich M 6 C carbides, while simultaneously reducing the volume fraction of Laves phase precipitates. Oxidation tests in steam (704 °C/1000 hours) showed that the Alloy 625 + WC nanocomposites exhibited slightly lower mass gain compared to the reference Alloy 625. In contrast, in the Ar + 0.25 pct SO 2 atmosphere, increasing WC content in Alloy 625 negatively affects the corrosion resistance due to the excessive formation of Ni 3 S 2 . The hardness of Alloy 625, initially measured at 201 HV10, increased to 254 HV10 with the addition of 5.0 pct WC, contributing to improved dry-sliding wear resistance.