Effect of Processing on Microstructure and Physical Properties of Three Nickel‐Based Superalloys with Different Hardening Mechanisms

Abstract

The nickel‐based superalloys Inconel alloy 600, Udimet alloy 720, and Inconel alloy 718 were produced by electron beam melting (EBM), casting, and directional solidification (DS). The distance between dendrites and the size of the precipitates indicated the difference in solidification rates between the three processes. In this study, the solidification rate was fastest with EBM, closely followed by casting, whereas it was much slower with DS. In the directional solidified materials the <100> direction was the fastest and thus, preferred growth direction. The EBM samples show a sharp (001)[100] texture in the building direction and in the two scanning directions of the electron beam. Macrosegregation was observed in some cast and directionally solidified samples, but not in the EBM samples. The melting temperatures are in good agreement with literature and the narrow melting interval of IN600 compare to UD720 and IN718 might reduce the risk of incipient melting during EBM processing. Porosity was observed in the EBM samples and the reasons are discussed. However, EBM seems to be a feasible process route to produce nickel‐based superalloys with well‐defined texture, no macrosegregation and a rapidly solidified microstructure.

Thermal effects on microstructural heterogeneity of Inconel 718 materials fabricated by electron beam melting

“…Strondl et al performed pioneering research on EBM processing of Inconel 718. [26][27][28] This work characterized fully dense EBM Inconel 718 using x-ray diffraction (XRD), transmission electron microscopy (TEM), and EBSD. XRD showed "very sharp" (100) texture in the build direction, and this texture remained pronounced after postprocess heat treatment.…”

Creep and oxidation kinetics at 1100°C of nickel-base alloys reinforced by hafnium carbides

“…Besides precipitation hardening and solid solution strengthening, cast polycrystalline nickelbased alloys may be reinforced by primary carbides resulting from final eutectic solidification. The carbides which are often present in cast superalloys are chromium carbides of the M 7 C 3 or M 23 C 6 types [27][28][29][30], to which other elements may also belong (tungsten, molybdenum…). These carbides are not stable at high temperature and they tend to partially, and sometimes totally, dissolve at temperatures as high as 1100°C.…”

Preparation of Inconel 740 superalloy by electron beam smelting

“…The traditional fabrication methods for superalloys are vacuum induction melting (VIM) plus vacuum arc remelting (VAR), powder metallurgy, Arcam's electron beam melting (EBM) process [1], electron beam solid freeform fabrication (EBSFF), and so on. The electron beam smelting technology is an effective method which is widely popularized for purifying solar-grade silicon [2], refining refractory metals and alloys [3], preparing high purity special steels and super clean steels, titanium and its alloys [4], and so on.…”