Effect of grit-blasting on the recrystallization behavior of DD6 single-crystal superalloy coated with NiCoCrAlYHf

The effect of grit-blasting on the recrystallization configuration of a single-crystal nickel-based DD6 superalloy has been investigated. Both coated (with NiCoCrAlYHf bond coat) and uncoated alloys exhibit a double-layered recrystallized microstructure consisted of the consecutive equiaxed recrystallization (ERX) layer and the inconsecutive cellular recrystallization (CRX) structure. A chemical gradient of gamma and gamma' phase promoting elements was observed in the interdiffusion zone, and the Cr profile was used to figure the average diffusion coefficient. With the increase of grit-blasting pressure, the overall recrystallization depth for both coated and uncoated alloys gradually increases at first, and then flattens out; the residual stress varies with the grit-blasting pressure in the same way.