Study of the Secondary Phases in Inconel 718 Aged Superalloy Using Thermodynamics Modeling

Abstract

The evaluation of stability of secondary phases in superalloys is of great importance because of its application under high homologue temperatures. The precipitation hardening Inconel 718 superalloy has high stress rupture and creep resistance, good LCF behavior and high corrosion resistance. Those properties can be obtained due to the high stable matrix based on Ni, Fe and Cr, as well as secondary phases promoters elements such as Ti, Al and Nb. This study aims to analyze the phase stability among a range of temperature from 500°C to approximately 1400°C. The thermodynamic modeling has a high importance to predict the behavior of alloys among equilibrium transition. The microstructure of the system was evaluated using Thermo-Calc software and the selected databases: SSOL4 and TTNI6. This analysis made possible the prediction of the phases presented, compositions and amounts. Results from SEM analysis were used to compare the results obtained, showing good coherence between them.

Microstructure and cavitation erosion performance of nickel-Inconel 718 composite coatings produced with cold spray

“…The aforementioned precipitates significantly contribute to the preservation of material properties at elevated temperatures [35], by hindering the movement of dislocations [36]. In addition the existence of the stable orthorhombic delta δ (Ni 3 Nb) phase [37], eta [38] η hexagonal ordered (Ni 3 Ti), sigma [38] (σ) phase, Laves phase [32,39], carbides and carbonitrides [40] as constituents of In718 has been reported depending on the heat treated condition. Moreover, several researcher have investigated their effects on the microstructure [41,42], mechanical properties [40] and corrosion performance [43] of the alloy.…”

Modification of Mechanical Properties in Directed Energy Deposition by a Static Magnetic Field: Experimental and Theoretical Analysis

“…Gamma phase is observed as the main phase in Figure 9 , which is also mentioned in [ 4 , 22 , 42 , 43 ]. The XRD analysis revealed no presence of Ni 3 (Al, Ti), Ni 3 Nb, and intermetallic Laves ((Ni, Cr, Fe) 2 (Nb, Mo, Ti)) phases [ 4 , 44 , 45 ]. As shown in Figure 9 , the intensity of the maximums varies, which can be explained by differences in texture.…”

Optimisation of sample geometry for thermo‐mechanical testing of precipitation hardenable nickel‐based superalloys with an ETMT machine

“…This grade of superalloy achieves its superior mechanical strength for high temperature applications from precipitation phases, predominantly made of Ni 3 Nb, with varying fractions of Ti and Al substituting for Nb in the form of Ni 3 (Al, Ti). [11,19,20] The δ-phase is the most stable form of Ni 3 Nb precipitates (≈700-1000 C) that usually nucleates intergranularly (i.e., at grain boundaries), with a possibility of intragranular nucleation (i.e., within grains) in the presence of γ 00 precipitate. γ 00 is the main strengthening phase in IN718 with thermodynamic stability over the 620-900 C temperature range and has the same chemical stoichiometry (i.e., Ni 3 Nb) as that of the δ-phase.…”