Dissolution of Nitrogen in Liquid Ni–Cr Superalloys

Abstract

The dissolution of nitrogen in liquid Ni–Cr alloys at 1773 and 1873 K over a wide range of composition has been determined by the constant pressure Sieverts' method. The nitrogen dissolution in these alloys is markedly increased with chromium content and decreased with temperature. The chromium effect on the nitrogen dissolution is described in terms of the Wagner's first and second order interaction parameters for both temperatures. © 1998 Canadian Institute of Mining and Metallurgy. Published by Elsevier Science Ltd. All rights reserved.

Résumé

En utilisant la méthode experimentale de Sieverts à pression constante, la dissolution de l'azote dans des alliages liquides Ni–Cr a été determinée pour un large domaine de composition aux températures de 1773 et 1873 K. La dissolution de l'azote augmente fortement avec la teneur en chrome et diminue avec la température. L'effet du chrome sur la dissolution a été decrit en termes de parametres d'interaction suivant le formalisme de Wagner. Ainsi, les coefficients du premier et du deuxième ordre entre l'azote et le chrome dans le nique1liquide ont été determiné pour le deux températures. © 1998 Canadian Institute of Mining and Metallurgy. Published by Elsevier Science Ltd. All rights reserved.     

Effect of Milling Parameters and Cr Content on Morphology and Solubility of Nanostructured Cu–Cr Solid Solutions

In the present work, a set of Cu-based powder mixtures containing up to 6 wt% Cr has been processed through mechanical alloying for a range of milling times up to 96 h. The mixtures were processed in a ball mill with ball to powder ratio of 10:1 and the equal numbers of 1 and 2 cm balls. The processed powder mixtures were investigated by scanning electron microscope, optical microscopic equipped with image analyzer, X-ray diffraction technique and micro hardness in order to determine the particles morphology, distribution of chromium, mean crystallite size, lattice parameter and hardness after milling, respectively. Crystallite sizes were measured by Williamson–Hall method and lattice parameters were determined using an extrapolation function. Results show that the powder behavior varies with milling time, and powder composition.     

Influence of the Oxygen Induced Surface Segregation Process of Solutes on the Anti-corrosion Properties of the Fe–Cr and Fe–Cr–Si Alloys

Metallurgical and Materials Transactions A - The influence of the oxygen-induced surface segregation process of Cr and Si solutes on the anti-corrosion properties of Fe–Cr and...     

Characterization of Fe–C–Cr Based Hardfacing Alloys

Hardfacing is one of the adaptable methods that can build up the hard and wear resistant surface layer of different materials on the surface of substrate material. It helps them withstand wear, as well as prevent corrosion and high temperature oxidation. In the present investigation three different types of Fe–C–Cr based hardfacing electrodes with varying chemical compositions were deposited on ASTM A36 steel substrate by using manual metal arc welding (MMAW) process. ASTM A36 steel was selected as a base material after consulting with Pressure and Process Boilers, Saharanpur (India), which is a leading manufacturer of boilers. ASTM A36 steel is mostly used by this company for the production of induced draft fans. MMAW process with direct current constant current type power source was used to deposit the hardfaced layers of uniform quality. Straight polarity was used for MMAW process so that more of the arc heat should be concentrated on the electrode. The hardfaced samples were characterized using various characterization techniques and the results of the same were also outlined in the present investigation.     

Spontaneous Pulverization Action of Mn–Al–Fe–Si Alloys and Effect of Addition Ti on the Stability

Systematical experiments have been carried out to investigate the mechanism of cracking and disintegration in the Mn–Al–Fe–Si master alloys. It revealed that pulverization of this alloy is due to the internal stress caused by volume change and hydrolysis. The earlier volume change associated with both the phase transition of Mn-content phase and the solidification process of ζ-FeSi₂ led to micro cracks. Through the micro cracks channel, the further volume change took place due to the Al₂O₃ expansion which was produced by the hydrolysis of aluminum phosphide and carbide when they contacted air. The two steps interacted with each other and led to complete disintegration of the alloys together. However it has been found that Ti can prevent the alloy hydrolysis due to the formation of stable titanium phosphide and carbide instead of the unstable aluminum phosphide and carbide, but it can not stop the earlier volume expansion.     

The Synthesis of Cast Materials Based on the MAX Phases in a Cr–Ti–Al–C System

Russian Journal of Non-Ferrous Metals - Two variants of the self-propagating high-temperature synthesis (SHS) process, namely, SHS from elements and SHS metallurgy, are combined to obtain cast...     

Phase Equilibria in Liquid Metal of the Cu–Al–Cr–O System

A thermodynamic analysis of phase equilibria in the Cu–Al–Cr–O system is carried out. Thermodynamic modeling of the liquidus surface of the Cu₂O–Al₂O₃–Cr₂O₃ oxide phase diagram is performed. To describe activities of an oxide melt, the approximation of the theory of subregular ionic solutions, the energy parameters of which were determined during modeling, is used. Melting characteristics of the CuCrO₂ compound are also evaluated in the course of the calculation. Coordinates of invariant equilibria points implemented in the Cu₂O–Al₂O₃–Cr₂O₃ ternary oxide system are established by the results of the calculation. Thermodynamic modeling of interaction processes in the Cu–Al–Cr–O system in occurrence conditions of a copper-based metal melt is also performed. The temperature dependence of the equilibrium constant of the reaction that characterizes the formation of the CuCrO₂ solid compound from components of the metal melt of the Cu–Al–Cr–O system is determined. The temperature dependence for the first-order interaction parameter (by Wagner) of chromium and oxygen dissolved in liquid copper is found. The results of thermodynamic modeling for the Cu–Al–Cr–O system are presented in the form of the solubility surface of components in metal, which makes it possible to attribute the quantitative variations in the metal melt concentration with qualitative variations in the composition of forming interaction products. It is determined by the results of modeling that particles of the |Al₂O₃, Cr₂O₃|_sol.sln solid solution are formed at valuable aluminum and chromium concentrations in the copper melt of the Cu–Al–Cr–O system as the main interaction product. The results of the investigation can be interesting for improving the technology process of smelting of chromium bronzes.     

Centrifugal Metallothermic SHS of Cast Co–Cr–Fe–Ni–Mn–(Х) Alloys

Russian Journal of Non-Ferrous Metals - A relatively new approach to obtaining metal materials containing several principal elements in equiatomic concentrations which look promising for replacing...     

Theoretical Investigation on Deoxidation of Liquid Steel for Fe–Al–Si–O System

Deoxidation of liquid steel involves consumption of high energy materials like ferro alloys and generation of deoxidation products which could be entrapped into liquid steel as non-metallic inclusions. The present investigation is focused on deoxidation of liquid steel, considering mainly aluminium and silicon as deoxidizer. A simple and realistic mathematical model of deoxidation of liquid steel has been developed based on the thermodynamic principles and material balance approach for day to day industrial practice. One of the main aims of the theoretical study was to predict the amount of deoxidizers required for a given steel composition. A methodology has also been developed to predict the stability of different oxides expected to be present in liquid steel after deoxidation. Model predictions have been compared with the industrial data as well as results obtained from commercial thermodynamic software package FactSage 6.4, simulated under identical conditions. Model predictions are in reasonable agreement with the ferro alloy consumption in industrial steelmaking processes.     

Solid–Liquid Interfacial Energy of Solid Neopentylglycol Solution in Equilibrium with Neopentylglycol–Aminomethylpropanediol Eutectic Liquid

The grain boundary groove shapes for solid neopentylglycol solution (NPG-40 mol pct AMPD) in equilibrium with the neopentylglycol (NPG)–aminomethylpropanediol (AMPD) eutectic liquid (NPG-42.2 mol pct AMPD) have been directly observed using a horizontal linear temperature gradient apparatus. From the observed grain boundary groove shapes, the Gibbs–Thomson coefficient (Г) and solid–liquid interfacial energy (σ _SL) of solid NPG solution have been determined to be (7.4 ± 0.7) × 10^?8 K m and (6.4 ± 1.0) × 10^?3 J m^?2, respectively. The grain boundary energy of solid NPG solution has been determined to be (12.5 ± 1.0) × 10^?3 J m^?2 from the observed grain boundary groove shapes. The ratio of thermal conductivity of equilibrated eutectic liquid to thermal conductivity of solid NPG solution has also been determined to be 0.48.     

Model of Calculating Activity of Nitrogen and Vanadium in FeCVN Molten Metal

The solubility of nitrogen in the FeCVN system was measured at 1 708 K and the model of calculating activity (action concentration) of nitrogen (N) and vanadium (V) was derived according to the phase diagram and the coexistence theory of the metal melt structure. The solubility expression of nitrogen in the FeCVN system at 1 708 K was wN=0058 194-0010 367wC+0005 543 4wV. Comparing the computing results with the experimental results, a satisfactory conclusion could be obtained. The analysis of the FeCVN system using this model showed that VN was present in a high temperature metal melt, which would reduce the action concentration of nitrogen obviously. It was consequently disadvantageous to the removal of nitrogen from hot metal.     

Effect of N,Mo, and Si on Local Corrosion Resistance of Unstabilized Cr–Ni and Cr–Mn–Ni Austenitic Steels

Metallurgist - Features of the effect of both individual and combined alloying with nitrogen, molybdenum and silicon of unstabilized cold-worked and heat-treated austenitic Cr–Ni and...     

Effect of Mn Content on Microstructure and Mechanical Properties of Fe–Mn–Cr–C High-Manganese Steels Produced Using Laser-Directed Energy Deposition

The microstructure and mechanical properties of high-manganese steel (HMnS) fabricated using laser-directed energy deposition (LDED) with Fe–Mn–4Cr–0.4C alloys with Mn contents of 13, 18.5, and 24 wt% are investigated. Additionally, the effect of annealing heat treatment on the microstructure and mechanical properties of the deposited HMnS is examined. Regardless of the manganese content, the deposited HMnS exhibits a fine microstructure without any defects (cracks or voids) and a strong fibrous texture along the <001>//building direction of the primary austenite phase. In addition, regardless of the manganese content, the grain size increases during annealing heat treatment, and the hardness decreases as the annealing temperature increases. The strength tends to decrease as the Mn content increases in the as-built state. In addition, regardless of the Mn content, the yield strength and ultimate tensile strength tend to decrease owing to the effect of annealing heat treatment. Although the maximum elongation of 18.5Mn and 24Mn does not change significantly upon heat treatment, the maximum elongation of 13Mn is greatly reduced by annealing. The deformation behavior of HMnS is characterized by transformation-induced plasticity (TRIP) for 13Mn and both TRIP and twinning-induced plasticity for 18.5Mn and 24Mn.     

Gallium–Germanium–Indium System: Excess Functions of Formaion of Liquid Alloys and Liquidus surface of Phase Diagram

Abstract

With a high temperature Calvet calorimeter, the enthalpies of formation of Ge-In and Ga-Ge-In liquid alloys have been measured between 703 and 1230 K.

A critical analysis of the excess functions of mixing and of the equilibrium phase diagrams of Ga-Ge, Ga-In and Ge-In alloys allows us to choose a set of consistent thermodynamic data for each bordering binary system.

The enthalpies of mixing of ternary alloys calculated by a phenomenological relation (Kohler equation) and measured by calorimetry are in good agreement.

From the Kohler equation are evaluated the partial excess functions of mixing and some temperatures of the liquidus of the phase digram.

Résumé

En utilisant un microcalorimètre Calvet, haute temp;amp;#x00E9;rature, no us avons déterminé des enthalpies de formation des alliages Ge-In et Ga-Ge-In entre 703 et 1230 K.

Une étude critique des fonctions thermodynamiques et des diagrammes d'équilibre des phases des trios systèmes binaires Ga-Ge, Ga-In et Ge-In nous a permis de proposer pour chacun d'eux un ensemble de fonctions d'excès de mélange cohérent avec le diagramme d' équilibre des phases.

A partir d'une relation polynomiale empirique faisant intervenir les enthalpies des binaires limitrophes, les enthalpies de mélange du systéme Ga-Ge-In ont été recalculées: l'accord étant satisfaisant, nous avons évalué les autres fonctions d'exces et déterminé la position de la surface du liquidus de ce système ternaire.