Abstract

In this study, Ni based superalloy powders (75% Ni, 20% Cr, 4% Al₂O₃, 0.6% Ti and 0.4% Y₂O₃), were mechanically alloyed for up to 8 h and were compacted and sintered at 1200°C. Sintered samples were hot-deformed at 1200°C for various amounts and secondary recrystallisation was applied at 1325°C for 1 h. Isothermal oxidation tests were conducted at 1000°C for up to 100 h in air. Surface morphology, fractured surface and chemical composition of the samples were analyzed by using x-ray diffraction (XRD) and scanning electron microscopy (SEM). Cr₂O₃ film formed on the surface of the samples after exposure in air. Weight change results indicated the samples gained a small weight by increasing the exposure time. All samples exhibited sub-parabolic oxidation behavior.

Key words: Mechanical alloying, powder metallurgy, oxidation, microstructure,superalloy.