Oxidation Behavior of Nickel-Base Single-Crystal Superalloy with Rhenium-Base Diffusion Barrier Coating System at 1,423 K in Air

摘要

The oxidation behavior of the nickel-base single-crystal superalloy TMS-82+ coated with a duplex Re(W)–Cr–Ni/Ni(Cr)–Al layer was investigated in air at 1,150 °C for up to 100 h. The coating layer was formed by electroplating Re(Ni) and Ni(W) films on the alloy, followed by Cr-pack cementation at 1,300 °C, and as a result, forming a continuous Re(W)–Cr–Ni diffusion-barrier layer. A Ni film containing fine Zr particles was then electroplated on the duplex layer, followed by Al pack cementation at 1,000 °C for 1 and 5 h to form an Al reservoir layer with a duplex Ni2Al3/γ-Ni layer, which changed quickly to γ-Ni phase containing (10～13)at.% Al for the 1 h Al-pack coat and a mixture of γ′-Ni3Al and β-NiAl phases for the 5 h Al-pack coat during high-temperature oxidation. A protective α-Al2O3 scale formed during oxidation at 1,150 °C in air, and parabolic rate constants of 7.4 × 10?11 and 6.6 × 10?10 kg2 m?4 s?1 were obtained for the 1 h- and 5 h-Al pack-coatings, respectively. There was little change in the structures of the superalloy substrate after oxidation at 1,150 °C in air for up to 100 h. It was found that the Re(W)–Cr–Ni layer remained stable, acting as a diffusion barrier between the alloy substrate and Al reservoir layers.