The Formation of SRZ on a Fourth Generation Single Crystal Superalloy Applied With Aluminide Coating

The formation behavior of Secondary Reaction Zone (SRZ) for a 4 th generation nickel-base single crystal (SC) superalloy with aluminide coating was investigated.The growth of SRZ is supposed to be dominantly controlled by the inward diffusion of aluminum from the coating layer to the substrate.The outward diffusion of Ru from the substrate to the coating layer may also contribute to SRZ formation.A remarkable reduction of SRZ was accomplished by depositing thin films composed of Co and/or Ru on the alloy surface prior to aluminide coating, that is expected to restrict the diffusion of Al and Ru between the coating layer and the substrate.