On the interdiffusion and precipitation of topologically close-packed phases in (Ni,Pt)Al coating/superalloy system: Effects of Pt and Ni contents in coating

Abstract In combination with the electroplating and electron beam physical vapor deposition (EB-PVD), four types of (Ni,Pt)Al coatings, namely Ni45Al, (Ni,Pt)45Al, Ni50Al, and (Ni,Pt)50Al were prepared. In order to study the interdiffusion and topologically close-packed (TCP) phases precipitation behavior, annealing experiments were carried out at 1100 °C for 20 h in vacuum. The addition of Pt layer has little effect on the thickness of interdiffusion zone (IDZ) because the inhibition effect of Pt on the Al diffusion weakens with the continuous diffusion of Pt. Meanwhile, the increase of Pt content in substrate promotes the Al diffusion. Besides, the effect of Pt on the TCP phases precipitation depends strongly on the Ni content in coating-For Ni45Al coating, adding Pt makes the volume fraction of TCP phases reduces from ~16.35 % to ~3.15 %, whereas this value is comparable in both Ni50Al and (Ni,Pt)50Al coatings (18.3 % and 17.9 %). This phenomenon is attributed to the competition mechanism between the acceleration effect of Pt on Al diffusion and the inhibition effect of Pt on TCP phases growth. The results provide a better understanding about the microstructure, especially the IDZ and TCP characteristics of (Ni,Pt)Al coating, which is significant for controlling the interdiffusion and TCP precipitation behavior in (Ni,Pt)Al coating.