THE EFFECT OF PACK-ALUMINISATION ON THE MICROSTRUCTURE OF MCRA1Y AND THE PERFORMANCE OF THERMAL BARRIER COATINGS

Plasma spraying and pack-aluminising processes were combined and applied to the nickel-base superalloy Mar-M247 to improve its cyclic oxidation resistance. The performance tests of duplex ZrO2-8 wt.%Y2O3/MCrAlY thermal barrier coatings (TBCs) were conducted at 1050-degrees-C, 1075-degrees-C, 1100-degrees-C, 1150-degrees-C and 1200-degrees-C. The results of the experiments in this study showed that TBC specimens with the aluminised MCrAlY bond coat exhibited higher cyclic lives (except for the Ni-22Cr-10Al-1Y bond coat), at all the temperatures tested, than specimens on which the bond coat was not aluminised. The microstructures of the Co-29Cr-6Al-1Y, Co-32Ni-21Cr-8Al-0.5Y and Ni-22Cr-1OAl-1Y bond coats with or without aluminising treatment were examined in detail using a scanning electron microscope equipped with an electron probe microanalyzer.