Oxygen incorporation in Ti2AlC MAX phases as bond coats: Multi-scale simulations for enhanced thermal shock resistance

초록

In thermal barrier coating (TBC) systems, MAX phases have emerged as potential alternatives to conventional metallic bond coats (BCs). Using multi-scale simulations, we examined how oxygen incorporation affects the high-temperature behavior of Ti2AlC. Although oxygen is typically considered harmful in BCs, Ti2Al(C1-xOx) showed different results that moderate oxygen incorporation lowers Young's modulus and increases the thermal expansion coefficient. This oxygen-induced softening effectively mitigates the large stiffness and thermal-expansion between the ceramic top coat and the superalloy substrate, thereby reducing thermal stress. Comparisons with CoNiCrAlY and (Ni,Pt)Al across several substrates showed that Ti2Al(C1-xOx) consistently produced lower stresses, particularly near the thermally grown oxide (TGO)-BC interface where failure usually initiates. These results indicate that oxygen incorporation, unavoidable in practical situations, can be used to tune Ti2AlC for improved reliability, supporting its use as a next-generation BC.

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