Laves phase and carbide precipitation mechanism of Inconel718 superalloy

doi:10.13251/j.issn.0254-6051.2024.03.032

Abstract

Abstract: In order to obtain the precipitation law of Laves phase and carbides of Inconel718 superalloy, the phase composition of the alloy in equilibrium was calculated using the nickel-based database in Thermal-Calc software. The microstructure and energy spectrum of the alloy were observed by means of optical microscope, scanning electron microscope and field emission electron probe microanalyzer, and the element segregation in the precipitated phase was explained. Finally, the melting and solidification process of the Inconel718 nickel-base superalloy was studied by using high-temperature laser confocal microscope (HT-CLSM). The results show that the phase transformation sequence of the Inconel 718 alloy during cooling is liquid phase, L+γ phase, L+γ+MC phase, L+γ+MC+δ phase, γ+MC+δ+η phase, γ+MC+δ+η+σ phase, γ+MC+δ+η+M₂₃C₆ phase; Ni, Cr and Fe elements in the alloy are mainly distributed in the dendrite trunk, showing negative segregation, while Nb element is mainly distributed in the interdendritic, showing positive segregation. The solidus temperature of the alloy is 1380 ℃. During the solidification process, with the increase of cooling rate, the temperature at which the alloy begins to solidify gradually decreases, the time required to achieve complete solidification decreases, and the liquid fraction also decreases with the increase of temperature. In addition, the whole solidification process is divided into initial, stable and final solidification stages according to the precipitation phase and microstructure changes during the solidification process. At the same time, the secondary dendrite spacing in the alloy is proportional to the third power of the cooling rate after solidification.

Key words: Inconel718 superalloy, precipitated phase, melting and solidification, secondary dendrite spacing, cooling rate

CLC Number:

TG132.3

Guo Xulong, Zhou Yang, Chen Qi. Laves phase and carbide precipitation mechanism of Inconel718 superalloy[J]. Heat Treatment of Metals, 2024, 49(3): 190-197.

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