Study of the Isothermal Oxidation Process and Phase Transformations in B2-(Ni,Pt)Al/RENE-N5 System

Changes in composition, crystal structure and phase transformations of B2-(Ni,Pt)Al coatings upon isothermal oxidation experiments (natural and scale free oxidation) at 1100 °C, as a function of time beyond their martensitic transformation, are reported. Specifically, the analysis of lattice parameter and composition are performed to identify changes in the B2-(Ni,Pt)Al phase upon the chemically-driven L10-(Ni,Pt)Al and L12-(Ni,Pt)3Al transformations. The B2-(Ni,Pt)Al phase was found to disorder and transform the martensite during the heat treatments for both oxidation experiments at approximately 36.3 and 40.9 at. % of Al, 47.7 and 42.9 at. % of Ni, 6.2 and 8.5 at. % of Pt, 4.2 and 2.9 at. % of Cr and 4.4 and 3.8 at. % of Co. The lattice constant and the long-range order parameter of the B2-(Ni,Pt)Al phase decreased linearly as a function of the elemental content irrespective of the nature of the oxidation experiments

Mass transfer study of a batch aluminum degassing ladle with multiple designs of rotating impellers

© 2018, The Minerals, Metals & Materials Society. A mathematical model has been developed to describe the mass transfer in a batch aluminum degassing ladle utilizing the rotor-injector technique. The model uses a Eulerian algorithm for the multiphase system and a dispersed renormalization group k–ε model to account for the turbulence in the system. The model was employed to evaluate the relative performance of the degassing kinetics of four impeller designs, i.e., nozzles with and without notches, and with four and five blades. The former two designs are commercially available, while the other two were proposed by the authors of this study. The results were validated against experimental measurements of the oxygen concentration in a physical model, and the flow pattern obtained was compared with image velocimetry. The model could satisfactorily predict the liquid velocity, gas holdup, vortex size and degassing kinetics, for the first time. The local kinetic parameter kLa predicted using the rigid model was found to be an important characteristic in terms of the degassing kinetics and depends on the bubble size distribution and the stirring of the liquid in the vessel. The proposed impeller designs help to distribute the bubbles more uniformly throughout the ladle, increasing momentum transfer from the impeller to liquid and thus improving gas–liquid mass transfer.status: Published onlin

Study of the Isothermal Oxidation Process and Phase Transformations in B2-(Ni,Pt)Al/RENE-N5 System

Changes in composition, crystal structure and phase transformations of B2-(Ni,Pt)Al coatings upon isothermal oxidation experiments (natural and scale free oxidation) at 1100 °C, as a function of time beyond their martensitic transformation, are reported. Specifically, the analysis of lattice parameter and composition are performed to identify changes in the B2-(Ni,Pt)Al phase upon the chemically-driven L10-(Ni,Pt)Al and L12-(Ni,Pt)3Al transformations. The B2-(Ni,Pt)Al phase was found to disorder and transform the martensite during the heat treatments for both oxidation experiments at approximately 36.3 and 40.9 at. % of Al, 47.7 and 42.9 at. % of Ni, 6.2 and 8.5 at. % of Pt, 4.2 and 2.9 at. % of Cr and 4.4 and 3.8 at. % of Co. The lattice constant and the long-range order parameter of the B2-(Ni,Pt)Al phase decreased linearly as a function of the elemental content irrespective of the nature of the oxidation experiments

Characterization of a C-Based Coating Applied on an AA6063 Alloy and Developed by a Novel Electrochemical Synthesis Route

This research aimed to obtain a C-based coating electrochemically applied on an AA6063 alloy. Two electrochemical cells were designed and manufactured to obtain the C-based coating film on flat and cylindrical samples. Structural and microstructural characterizations were performed along with fatigue and corrosion performance testing. The structural and microstructural characterization revealed that the C-based coating deposited on AA6063 corresponded to carbon nanofibers and/or polycrystalline graphite. The performance testing showed an increase in fatigue life along with a decrease in corrosion resistance. The fracture surfaces of the fatigued samples were inspected by Scanning Electron Microscopy and 3D optical microscopy to correlate them with fatigue life estimation. The aforementioned process is a step towards the future development of a complete coating system that will overcome corrosion susceptibility. The carbon film obtained by this electrochemical route has not previously been reported elsewhere