Impact of Ru buffer layer on diffusion behavior between NiCoCrAlY and single crystal superalloy DD6

In this paper, a metallic protective coating is investigated as a diffusion barrier on the second generation single crystal superalloy DD6. A double layer of NiCoCrAlY/Ru coating is prepared by electroplating and electron beam physical vapor deposition (EB-PVD) on a sample of single crystal superalloy DD6. Also, a single NiCoCrAlY coating is deposited onto the single crystal superalloy by EB-PVD. The results show that an interdiffusion zone (IDZ) of ~55 μm and a secondary reaction zone (SRZ) of ~25 μm are formed in the superalloy after 300 h heat-treatment at 1050°C in atmospheric environment. Compared with the single NiCoCrAlY coating, the NiCoCrAlY/Ru coating effectively suppressed the formation of SRZ in the superalloy. There are only tiny amounts of topologically close-packed phases (TCP) precipitated in the superalloy.