Cyclic oxidation of coated and uncoated single-crystal nickel-based superalloy MC2 analyzed by continuous thermogravimetry analysis

Abstract

The previously developed cyclic thermogravimetry analysis (CTGA) [Monceau D, Poquillon D. Oxid Met 2004;61:143–163] method is applied to the cyclic oxidation at 1150 C of a NiCoCrAlYTa-coated and an uncoated single-crystal nickel-based superalloy MC2. A new procedure to correct the buoyancy effect is proposed in order to evaluate the amount of oxide formed during the heating periods, which can be important for alloys forming fast-growing transient oxides or during cycling with slow heating rates. It is shown that cyclic thermogravimetry is an useful technique for uantifying the oxidation resistance of an industrial alloy. Moreover, the behaviour of the alloy is better described with CTGA than with a classic cyclic gravimetric test, because both isothermal oxidation kinetics and spalling behaviour are assessed independently. In the present case, it is shown clearly that the NiCoCrAlYTa coating greatly improves the cyclic oxidation resistance without decreasing the isothermal oxidation kinetics. Finally, the use of CTGA for performance and time-of-life evaluations is demonstrated.