Ambient and 550 °C tribological behavior of select MAX phases against Ni-based superalloys

In this paper, we report on the tribological behavior, at 25 and 550 °C of the following layered (MAX phase) ternary carbides: Ti2AlC, Cr2AlC, Ta2AlC, Ti3SiC2, Ti2AlN, Ti4AlN3, Cr2GeC, Cr2GaC, Nb2SnC and Ti2SnC, tested against Ni-based superalloys, SA (Inconel-718 and Inconel-600). The tests were performed using a pin-on-disc method at 1 m/s and 3 N. At room temperature, the wear rates, WRs, were relatively high (≥10−4 mm3/N-m) and no correlation was found between the WRs and the friction coefficients, μ. Third body abrasion is believed to be responsible for the high WRs at this temperature. At 550 °C, oxidized transfer films were identified on both contact surfaces. The tribofilms comprised mostly of Ni, Cr, Fe and O and resulted in low (<10−6 mm3/N-m) WRs and μʹs < 0.5. This result implies that the tribo-oxidation products of the Ni-based SA tested herein (Inconel 718) are lubricious.