Enhancement on thermal shock resistance of TBCs with EP interlayer

Abstract

YSZ thermal barrier coatings (TBCs) were sprayed onto 2A70 aluminium by atmospheric plasma spray. To relieve the thermal stress between TBCs and aluminium substrate, Ni–P and Ni–Cu–P electroless plating (EP) were deposited onto aluminium as interlayers. The fabricated Ni–P and Ni–Cu–P EPs exhibited amorphous structure and their crystallisation temperatures were 346·4 and 356·4°C, respectively. Deposition of the interlayers did not degrade much the bonding strength of the TBCs. The thermal shock lifetimes of TBCs with Ni–P interlayer and Ni–Cu–P interlayer were approximately 600 and 200 cycles, respectively, which were enhanced compared to that of the conventional TBCs (58 cycles). The failure of the TBCs with Ni–Cu–P interlayer was mainly caused by the thermal mismatch stress induced during the thermal shock, while the TBCs with Ni–P interlayer failed due to the interdiffusion between the interlayer and the substrate and the relatively poor ductility of the Ni–P interlayer.