“…A similar phenomenon which is called 'bi-phase' formation has been reported by Sinha et al in ODS IN617 alloys [43]. This has been attributed to the formation mechanisms of the Y-Al-O particles due to the reaction between Y2O3 and Al2O3 [44]. In other words, the existence of such particles infers incomplete transformation due to rapid cooling during SLM production.…”
Oxide dispersion strengthened (ODS) Ni-based alloys having a high density of nano-oxides (NOs) (<10 nm) are considered to be good candidates for extreme environments, such as high temperature, radiation, and corrosion. In this study, ODS IN718 alloys have been produced using conventional powder metallurgy (PM) and novel selective laser melting (SLM) additive manufacturing. The effect of processing routes on the microstructure, in particular on the nano-oxide formation and structure has been investigated. It has been found that the powder metallurgy method that consists of compressing followed by sintering at 1250 and 1500 °C results in a nano-granular structure with homogenously distributed fine nano-oxides having a high number density. Similarly, SLM results in a high number density of fine nano-oxides; however, the particles exist in groups with the grains/cells. The nano-oxides are determined to be Y2Ti2O7, Y2TiO5 or YTiO3 and Y-Al-O. The deviation in the lattice parameters of Y2Ti2O7 infers the existence of some Al in the structure. This study sheds light on producing ODS IN718 alloys with high-density nano-oxides using powder metallurgy and additive manufacturing methods.
“…A similar phenomenon which is called 'bi-phase' formation has been reported by Sinha et al in ODS IN617 alloys [43]. This has been attributed to the formation mechanisms of the Y-Al-O particles due to the reaction between Y2O3 and Al2O3 [44]. In other words, the existence of such particles infers incomplete transformation due to rapid cooling during SLM production.…”
Oxide dispersion strengthened (ODS) Ni-based alloys having a high density of nano-oxides (NOs) (<10 nm) are considered to be good candidates for extreme environments, such as high temperature, radiation, and corrosion. In this study, ODS IN718 alloys have been produced using conventional powder metallurgy (PM) and novel selective laser melting (SLM) additive manufacturing. The effect of processing routes on the microstructure, in particular on the nano-oxide formation and structure has been investigated. It has been found that the powder metallurgy method that consists of compressing followed by sintering at 1250 and 1500 °C results in a nano-granular structure with homogenously distributed fine nano-oxides having a high number density. Similarly, SLM results in a high number density of fine nano-oxides; however, the particles exist in groups with the grains/cells. The nano-oxides are determined to be Y2Ti2O7, Y2TiO5 or YTiO3 and Y-Al-O. The deviation in the lattice parameters of Y2Ti2O7 infers the existence of some Al in the structure. This study sheds light on producing ODS IN718 alloys with high-density nano-oxides using powder metallurgy and additive manufacturing methods.
“…As the Al diffuses through the matrix, it is believed to form Al 2 O 3 by reacting with the excess oxygen in the matrix and the ambient and sticks to the yttria particle. Y 2 O 3 and Al 2 O 3 react to form the Y–Al–O complex oxides and sometimes the matrix elements also enter their lattice (Sivakumar et al, 2021). Fig.…”
Section: Resultsmentioning
confidence: 99%
“…Subsequently, the milled powders were consolidated using a Dr. Sinter SPS-5000, Fuji Electronic Industrial Co., Japan. 50 MPa pressure was applied with a graphite cylindrical die at 1,100°C for consolidation with a hold time of 10 min (Sivakumar et al, 2021). The sample was annealed at a typical service temperature of 1,050°C for 10 h. A conventional Jet-thinning process was used to prepare TEM ready samples.…”
Nanocrystalline oxides are mainly responsible for Ni-base oxide dispersion strengthened (ODS) superalloys excellent thermo-mechanical properties. To establish the microstructural correlations between the metallic matrix and various oxide dispersoids, we report here the atomic-scale structure and chemistry of the complex nano-oxide dispersoids. Ultrahigh-resolution Cs-aberration-corrected scanning transmission electron microscopy (STEM) based techniques have been used to resolve nano-dispersoids in the Alloy 617 ODS. These nano-oxides, interestingly, possess a variety of high-angle annular dark-field (HAADF) contrasts, that is, bright, dark, and bi-phases. Both the light and heavy atoms have been found to be present in Y–Al–O complex-oxide nanostructures in varying quantities and forming a characteristic interface with the metallic matrix. In overcoming the limitation of conventional STEM-HAADF imaging, the integrated differential phase-contrast imaging technique was employed to investigate the oxygen atoms along with other elements in the dispersoids and its interface with the matrix. The most intriguing aspect of the study is the discovery of a few atoms thick Al2O3 interlayer (shell) around a monoclinic Y–Al–O core in the Ni-matrix. On the other hand, when the dispersoid is a hexagonal type Y–Al–O complex, the interface energy is already low, maintaining a semi-coherent interface and it was devoid of a shell.
“…The enthalpy method was adopted to save the amount of experiment and storage space. The enthalpy method refers to the integral of density multiplied by the specific heat capacity with respect to temperature, as shown in Equation (5). Then, the enthalpy was compensated to Equation ( 4…”
Section: Latent Heat Of Phase Changementioning
confidence: 99%
“…It is mainly used in industrial and aviation steam turbine hot-end parts [1][2][3]. In the face of a complex working environment and product upgrade requirements, its oxidation and corrosion resistance under high-temperature conditions cannot fully meet the higher use requirements of the new generation of hot-end components [4,5]. Inconel617 alloy can meet the more stringent performance requirements as much as possible by electron beam cladding material surface modification and repair engineering.…”
To better control the Inconel617 electron beam cladding solidification process, a three-dimensional temperature field model was built to simulate the temperature gradient, cooling rate, and solidification rate in the solidification process and take a deep dive into the solidification behavior, as well as the calculation of the solidification characteristic parameters at the edge of the molten pool and then predict the solidification tissue structure. The study shows that the largest temperature gradient occurred in the material thickness direction. The self-cooling effect of the material dominated the solidification of the alloy layer; the cooling rate depended on the high-temperature thermal conductivity of the material and the self-cooling effect of the matrix, and the maximum cooling rate in the bonding zone was 1380 °C/s. The steady-state solidification rate was equal to the moving speed of the heat source; the solidification characteristics of the solidification process at the edge of the molten pool increased with the distance from the surface: the cooling rate decreased from 1421.61 to 623 °C/s, the temperature gradient increased from 0.0723 × 106 to 0.417 × 106, and the solidification rate decreased from 0.01 to 0 m/s. The prediction was made that the small and thin equiaxed crystals are on the top, a thin and short dendritic transition structure in the middle, and relatively coarse dendrites at the bottom. Experiments confirmed that the solidification tissue structure is basically consistent with the simulation law.
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