TEM and X-Ray Examinations of Intermetallic Phases and Carbides Precipitation in an Fe-Ni Superalloy during Prolonged Ageing

Abstract:

The influence of prolonged ageing on the precipitation process of the secondary phases in an Fe-Ni superalloy of A-286 type has been studied. The samples were subjected to a solution heat treatment at 980°C for 2 h and water quenched, and then aged at temperatures of 715, 750 and 780°C at holding times from 0.5 to 500 h. Structural investigations were conducted using TEM and X-ray diffraction methods. The X-ray phase analyses performed on the isolates were obtained by anodic dissolution of the solid samples. After solution heat treatment the alloy has the structure of twinned austenite with a small amount of undissolved precipitates, such as carbide TiC, carbonitride TiC_0.3N_0.7, nitride TiN_0.3, carbosulfide Ti₄C₂S₂, Laves phase Ni₂Si, and boride MoB. The application of ageing causes precipitation processes of γ-Ni₃(Al,Ti), G (Ni₁₆Ti₆Si₇), η (Ni₃Ti), β (NiTi) and σ (Cr_0.46Mo_0.40Si_0.14) intermetallic phases, as well as the carbide M₂₃C₆. It was found that the main phase precipitating during alloy ageing was the γ intermetallic phase.

• Periodical: Solid State Phenomena (Volume 212)
• Pages: 15-20
• DOI: https://doi.org/10.4028/www.scientific.net/SSP.212.15
• Online since: December 2013
• Authors: Kazimierz J. Ducki, Jacek Mendala, Lilianna Wojtynek
• Keywords: A-286 Alloy, Intermetallic Phase, Precipitation, TEM, X-Ray Analysis

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