Effect of Coating Pre-Treatment on Surface Recrystallization of DD6 Single Crystal

Thermal barrier coatings (TBCs) are widely used to protect high-temperature components against harsh environments, such as extremely high temperatures. In this work, a second generation Ni-based single crystal superalloy (DD6) was treated in two ways: (1) via simple surface sandblasting under different pressures with no additional coating, and (2) through simple surface sandblasting under different pressures and then by applying NiCoCrAlYHf (HY5) coatings. The effects of pre-treatment (sandblasting) and the HY5 coating on the surface recrystallization of the alloy were thoroughly investigated. According to the results, both sandblasting pressure and the presence or absence of a coating significantly influence surface recrystallization. In particular, the critical sandblasting pressure for recrystallization increased the maximum recrystallization depth in both the coated and uncoated samples. Meanwhile, the recrystallization depth of the alloy with a coating was reduced compared to that without a coating. In addition, the number of recrystallized cells in the coated alloy was decreased, which indicated that the HY5 coating effectively reduced the degree of recrystallization.