Tribology International ( IF 4.271 ) Pub Date : 2020-01-03 , DOI: 10.1016/j.triboint.2019.106155 Ahmed Korashy, Helmi Attia, Vince Thomson, Saeid Oskooei
Superalloys are extensively used in the design of combustor components of aero engines because they can withstand high temperature oxidizing environments, while maintaining their strength. This investigation aims at assessing the tribological characteristic of some combustor components candidate cobalt-based and nickel-based superalloys. Three combinations of the alloys were tested at different operating conditions and temperatures; CP1 (Cobalt 1/Cobalt 2), CP2 (Cobalt 2/Nickel 1) and CP3 (Cobalt 1/Nickel 1). The investigation showed that the increase in temperature from 350 °C to 550 °C was associated with a decrease in the coefficient of friction for all tested contact pairs, a decrease in wear coefficient (wear damage) for CP1, and an increase in wear coefficient for CP2 and CP3. Samples analysis using SEM-EDS and Raman Spectroscopy showed that the least wear coefficient exhibited by CP1 at 550 °C, and by CP2 at 350 °C is due to the development of a compacted protective layer of chromium oxide Cr2O3, known for its favourable tribological characteristic, which contributes to load bearing, precludes the metal-metal contact, and reduces the friction and wear damage. On the other hand, the decrease in friction was associated with an increase in wear coefficient for CP2 and CP3 due to the formation of a porous oxide layer with high tungsten trioxide (WO3) content which makes the oxide softer, decreases friction and increases the wear damage in the oxide layer. Material selection maps are presented to aid aero-engine designers.