The influence of Pt on the element diffusion behavior at the interface of Ni-Al alloys and a single crystal superalloy

The Pt-modified Ni-Al coatings demonstrate exceptional high-temperature oxidation resistance. However, elemental interdiffusion at the coating/alloy interface can lead to degradation of the interface microstructure. This study investigates the influence of Pt on the interdiffusion behavior at the interface of Ni-Al coating alloys and a single crystal superalloy. Single-phase Ni-Al/Ni-Al-Pt alloys (designated as Ni-50Al, Ni-40Al, Ni-50Al-10Pt, and Ni-40Al-10Pt, in at. %) and two-phase Ni-Al/Ni-Al-Pt alloys (designated as Ni-30Al and Ni-30Al-10Pt, in at. %) were prepared and used to form diffusion couples with an experimental single crystal superalloy. The interdiffusion coefficients were calculated after diffusion in a vacuum environment. The results indicate that the addition of Pt decreases the defect formation energy in both the NiAl and Ni₃Al phases, leading to increased interdiffusion coefficients in the Ni-50Al/SCA21 and Ni-40Al/SCA21 diffusion couples. However, the overall interdiffusion coefficients for Al show little variation before and after the addition of Pt in the Ni-30Al/SCA21 diffusion couples. This can be attributed to the reduced chemical potential of Al at the Ni-30Al-10Pt side. Additionally, Pt modification also reduces the interfacial energy and strain energy associated with new phase precipitation, resulting in increased density and decreased average size of the precipitates at the interface.