Abstract: The surface of single crystal superalloy was pretreated by grit blasting, and the NiCoCrAlYHf coatings were then fabricated on the superalloy substrates by vacuum arc plating technique. The effect of grit blasting on the recrystallization and elemental diffusion behaviors of substrates after isothermal oxidation was investigated in detail. The microstructure and elemental contents of the samples with and without coatings, as well as their interaction mechanisms with recrystallization behavior, were systematically analyzed by SEM and EDS. The results indicate that the recrystallization sizes of the substrate and coating samples gradually increase with the increment of the grit blasting strengths. The coating specimens show no cellular recrystallization when the grit blasting strength is set to be 0.2MPa. However, the function of recrystallization inhabitation of the coatings gradually decreases with the increment of the grit blasting strengths from 0.3MPa to 0.7MPa. The phenomenon of recrystallization was not observed at the interface between the coating and the substrate after thermal exposure at 1100℃ for 250h. Meanwhile, there was no obvious fluctuation of the elemental concentration at the interface, and the contents of the elements on the interface tend to be smooth.

Key words: single crystal superalloy, recrystallization, grit blasting, coating, elemental diffusion