As-cast microstructure, wear and oxidation resistance of Alloy 718+TiC nanocomposites processed via suction casting

In response to the increasing demand for materials capable of withstanding harsh service conditions at elevated temperatures, this study presents a strategy to enhance the performance of Alloy 718. Ex-situ nanocomposites of Alloy 718 with varying TiC content (1.25, 2.5, 3.75 or 5.0 wt %) were produced through mechanical alloying followed by suction casting. The introduced TiC nanoparticles reacted with Alloy 718, influencing phase transformation temperatures and the resulting microstructure. The dendritic regions in both the Alloy 718 and the TiC-reinforced composites primarily consisted of the γ-matrix, while interdendritic areas contained MC-type carbides and Laves phase precipitates. Synchrotron radiation analysis and microstructural observations revealed that the partial dissolution of TiC promoted the formation of Ti,Nb-rich carbides and simultaneously reduced the amount of Laves phase during solidification. Oxidation tests in steam and an Ar+0.25 % SO 2 mixture (704 °C/1000 h) showed that the Alloy 718+TiC nanocomposites experienced lower mass gain compared to the unreinforced Alloy 718, indicating enhanced oxidation resistance. The presence of TiC improved the alloy's stability in the SO 2 -containing environment by suppressing the formation of Ni 3 S 2 particles. The hardness of Alloy 718, initially measured at 201 HV10, increased to 244 HV10 with the addition of 5.0 % TiC, contributing to improved wear resistance, which give a perspective to use these materials for repair of turbine blades susceptible to wear during service.