The interfacial stability of single crystal superalloy affected by the phase structure of the Ni-Al coating

Interfacial stability between the bond coating and single crystal superalloy substrate is crucial for their long-term performance at elevated temperatures. Herein, we designed coatings with various phase structures and used the typical single crystal superalloy Rene ' N5 as the substrate to investigate the intrinsic mechanism underpinning recrystallization using experiments combined with atomistic simulations. Experimentally, recrystallization occurred in the specimen with coatings of medium Al content (CA-25 specimen); in contrast, there was no secondary reaction zone in the CA-30 specimen with coatings of the highest Al content. From simulations, the nudged elastic band calculation demonstrated that a higher energy barrier (Delta E0) was required for new grain nucleation in the substrate under beta-NiAl grains, which existed in the CA-30 coating. Our findings provide a fundamental understanding of interfacial stability and benefit the design of bond coatings for superalloys.