Papers by Keyword: Ni-Al-Pt

Abstract: High temperature cyclic oxidation behavior of γ'-base Ni-25Al-10Pt (in at.%) alloy was investigated at 1000°C in air with and without 30vol.%H₂O. The oxidation mass gain during the initial stage of oxidation was similar in both atmospheres, but the oxidation rate in air+H₂O was lower in the longer steady-state oxidation stage. Metastable Al₂O₃, which formed during the initial stage of oxidation, transformed completely after about 100hr of oxidation in dry air. The transformation to α-Al₂O₃ also occurred in air+H₂O, but complete transformation to α-Al₂O₃ was not observed during the oxidation time in the present study. θ-Al₂O₃ grains remained for longer on the α-Al₂O₃ layer in air+H₂O and became significantly coarser with oxidation time. The present results indicate that water vapor delays the metastable to α-Al₂O₃ phase transformation, and decreases the growth rate of α-Al₂O₃.

Abstract: Aluminide diffusion coatings act as a remedy against the aggressive environments in which modern aero-gas turbines operate. Platinum addition to basic aluminide coatings significantly improves the oxidation resistance of these coatings. The increase in operating temperatures of industrial energy systems and gas turbines, has led to the extensive use of coatings capable of providing improved service life. Interdiffusion plays a critical role in understanding the integrity of such coatings. The Danielewski-Holly model of interdiffusion which allows for the description of a wide range of processes (including processes stimulated by reactions at interfaces) is employed for studying of interdiffusion in the Pt-modified β-NiAl coatings. Using the inverse method the intrinsic diffusivities of Ni, Al and Pt were calculated. Such obtained diffusivities were subsequently used for modelling of thermal stability of Pt-modified aluminide coatings in air and in argon atmosphere.