Effect of water vapor on tribological performance of Inconel 718 at different conditions for next-generation gas turbine engine

Nickel-based superalloys (e.g., Inconel 718) are widely used in the aerospace industry due to their high temperature constancy in terms of mechanical properties and chemical stability. With the recent advances in sustainable aviation, there is a strong desire to better understand their compatibility with hydrogen combustion or water vapor in gas turbine engines. Therefore, this study investigated the tribological behavior of Inconel 718 under dry and water vapor conditions at various temperatures. The reciprocating ball on flat type tribometer was used to perform friction tests on Inconel 718 against alumina and Inconel 718 counterballs in the absence or presence of water vapor at room and elevated temperatures. The results showed that water vapor caused a reduction in the friction and wear at room and elevated temperatures against the Alumina mating surface, when compared to the tests performed under dry conditions. The low friction and wear in water vapor was attributed to the formation of an aluminum trihydroxide (bayerite—Al(OH) 3 ) tribofilm. On the other hand, Inconel 718 vs. Inconel 718 showed higher wear in the presence of water vapor at RT compared to that in dry conditions. Conversely, water vapor decreased wear at HT compared to HT dry. The higher wear was attributed to the lack of sufficient lubricious oxides formation on the wear tracks for Inconel 718 vs. Inconel 718 at HT.