High Temperature Oxidation Behavior of Selective Laser Melting Manufactured IN 625

Abstract

The high-temperature oxidation behavior of selective laser melting (SLM) manufactured IN 625 was studied over 96 h of exposure at 900 °C and 1050 °C in air. An extensive analysis was performed to characterize the oxide scale formed and its evolution during the 96 h, including mass gain analysis, EDS, XRD, and morphological analysis of the oxide scale. The mass gain rate of the bare material increases rapidly during the first 8 h of temperature holding and diminishes at higher holding periods for both oxidation temperatures. High-temperature exposure for short periods (24 h) follows a parabolic law and promotes the precipitation of δ phase, Ni-rich intermetallics, and carbides. Within the first 24 h of exposure at 900 °C, a Cr2O3 and a (Ni, Fe)Cr2O4 spinel scale were formed, while at a higher temperature, a more complex oxide was registered, consisting of (Ni, Fe)Cr2O4, Cr2O3, and rutile-type oxides. Prolonged exposure of IN 625 at 900 °C induces the preservation of the Cr2O3 scale and the dissolution of carbides. Other phases and intermetallics, such as γ, δ phases, and MoNi4 are still present. The exposure for 96 h at 1050 °C led to the dissolution of all intermetallics, while the same complex oxide scale was formed.

Manufacturing of Closed Impeller for Mechanically Pump Fluid Loop Systems Using Selective Laser Melting Additive Manufacturing Technology

“…Additionally, the influence of process parameters on the specimen surface roughness and material hardness was assessed. The main conclusion was that for 250 W laser power, 700-800 mm/s scan speed, and layer thicknesses in the range of 30-50 µm, the relative densities achieved are over 99.5%, as highlighted by the authors in [30][31][32]. However, during the manufacturing of the closed impeller and due to the appearance of the adherent dross on the interior side of the impeller, subjected to analysis in [33], the laser power was decreased to 200 W, which was found to be the best corrective measure.…”

Optimization on Temperature Strategy of BOF Vanadium Extraction to Enhance Vanadium Yield with Minimum Carbon Loss

“…As the molten bath temperature increasing continuously, there was a temperaturemade ∆G of reaction (2) equal to (6). It stood for the thermodynamic equilibrium of vanadium removal and reduction, as shown in Figure 3 [11,12].…”

“…The removal of C is prior to V in this period, and (V2O3) in the slag also was reduced by C, as shown in Figure 3. However, △G of reaction (2) was still less than (6), which meant the thermodynamic driving force of vanadium removal was greater than the reduction. V removal and reduction of (V2O3) exist simultaneously.…”

“…Carbon monoxide (CO) was considered as the oxidative product of C as it was saturated in molten iron (≥3.4 wt%). In addition, vanadium trioxide (V 2 O 3 ) would be reduced by C, as displayed in Equation (6). The standard Gibbs free energies (∆G θ ) of reaction (1), ( 2) and ( 6) with various temperatures were showed as follows Figure 3.…”

“…The selective oxidation temperature between carbon and vanadium, T sl, a thermodynamic temperature, used to be considered as a key to ensure smelting steps. It related to the transformation from preferential V removal to C [5,6]. Most studies tend to the selective oxidation theory, which required the molten bath temperature never went beyond T sl [4].…”