The influence of yttrium alloying on mechanical properties of superalloy 718

Superalloy 718 is a precipitation hardened, high strength nickel-base, metallic alloy widely used as structural components for aerospace, oil and gas and energy industries. It can operate under harsh environments and high temperature (up to circa 650^o C). Despite the outstanding properties, there is a continuous drive for improvement of its operational performance, through various strategies, like processing improvement, alloying and microstructural control, that can be correlated.

One of the various research lines for the improvement of superalloy's microstructure and properties is based on controlled additions of rare earths. Among then, yttrium has shown a strong potential, with promising results on improving the alloy's cleanliness, microstructure and properties like creep and hydrogen embrittlement resistance. However, its addition is limited and tricky and shall be carefully controlled during further processing. This is even more prominent when considering the fabrication of cast and wrought components.

In this regard, the present work presents the result from microstructural characterization and mechanical tests of Y-added superalloy 718 under different degrading conditions, like high temperature and hydrogen embrittlement and compared alloy 718 with no Y-alloying. The results show that a controlled yttrium addition was beneficial to the overall ductility of the alloy, without impairing its high strength.