Fluxing of protective oxide scales on superalloys via a thermal surface tension gradient

1983 ◽  
Vol 18 (12) ◽  
pp. 3743-3748 ◽  
Author(s):  
S. K. Lau ◽  
S. C. Singhal
Keyword(s):  
Surface Tension ◽  
Surface Tension Gradient ◽  
Oxide Scales ◽  
Protective Oxide

scholarly journals Exploring the Effect of Silicon on the High Temperature Corrosion of Lean FeCrAl Alloys in Humid Air

2021 ◽  
Author(s):  
T. Sand ◽  
A. Edgren ◽  
C. Geers ◽  
V. Asokan ◽  
J. Eklund ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
High Temperature ◽  
Oxidation Behavior ◽  
High Temperature Corrosion ◽  
The Other ◽  
Oxide Scales ◽  
Protective Oxide ◽  
New Approach ◽  
Fecral Alloys ◽  
Cr Evaporation

AbstractA new approach to reduce the chromium and aluminium concentrations in FeCrAl alloys without significantly impairing corrosion resistance is to alloy with 1–2 wt.% silicon. This paper investigates the “silicon effect” on oxidation by comparing the oxidation behavior and scale microstructure of two FeCrAl alloys, one alloyed with silicon and the other not, in dry and wet air at 600 °C and 800 °C. Both alloys formed thin protective oxide scales and the Cr-evaporation rates were small. In wet air at 800 °C the Si-alloyed FeCrAl formed an oxide scale containing mullite and tridymite together with α- and γ-alumina. It is suggested that the reported improvement of the corrosion resistance of Al- and Cr-lean FeCrAl’s by silicon alloying is caused by the appearance of Si-rich phases in the scale.

Breakdown of Evaporating Falling Films as a Function of Surface Tension Gradient

1996 ◽  
Vol 17 (4) ◽  
pp. 72-81 ◽  
Author(s):  
ALI G. BUDIMAN ◽  
C. FLORIJANTO ◽  
J. W. PALEN
Keyword(s):  
Surface Tension ◽  
Surface Tension Gradient ◽  
Falling Films

scholarly journals Effect of a surface tension gradient on the slip flow along a superhydrophobic air-water interface

2018 ◽  
Vol 3 (3) ◽  
Author(s):  
Dong Song ◽  
Baowei Song ◽  
Haibao Hu ◽  
Xiaosong Du ◽  
Peng Du ◽  
...  
Keyword(s):  
Surface Tension ◽  
Slip Flow ◽  
Surface Tension Gradient ◽  
Water Interface ◽  
Air Water Interface

Numerical Simulation of Oil-Droplet Cleavage by Surfactant

1996 ◽  
Vol 118 (2) ◽  
pp. 201-209 ◽  
Author(s):  
Xiaoyi He ◽  
Micah Dembo
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Surface Tension ◽  
Large Deformation ◽  
Concentration Gradient ◽  
Surface Tension Gradient ◽  
Oil Droplets ◽  
Numerical Computations ◽  
Oil Droplet ◽  
Pure Surface

We present numerical computations of the deformation of an oil-droplet under the influence of a surface tension gradient generated by the surfactant released at the poles (the Greenspan experiment). We find this deformation to be very small under the pure surface tension gradient. To explain the large deformation of oil droplets observed in Greenspan’s experiments, we propose the existence of a phoretic force generated by the concentration gradient of the surfactant. We show that this hypothesis successfully explains the available experimental data and we propose some further tests.

scholarly journals Tackling the Short-Lived Marangoni Motion Using a Supramolecular Strategy

CCS Chemistry ◽  
2019 ◽  
Vol 1 (2) ◽  
pp. 148-155 ◽  
Author(s):  
Mengjiao Cheng ◽  
Dequn Zhang ◽  
Shu Zhang ◽  
Zuankai Wang ◽  
Feng Shi
Keyword(s):  
Surface Tension ◽  
Electricity Generation ◽  
Adsorption Equilibrium ◽  
Molecular Level ◽  
Surface Tension Gradient ◽  
Aggregation State ◽  
Physical Limit ◽  
Competitive Kinetics ◽  
Air Liquid Interface ◽  
Spontaneous Motion

Inspired by the intriguing capability of beetles to quickly slide on water, scientists have long translated this surface-tension-gradient–dominated Marangoni motion into various applications, for example, self-propulsion. However, this classical spontaneous motion is limited by a short lifetime due to the loss of the surface tension gradient. Indeed, the propellant of amphiphilic surfactants can rapidly reach an adsorption equilibrium and an excessive aggregation state at the air/liquid interface. Here, we demonstrate a supramolecular host–guest chemistry strategy that allows the breaking of the physical limit of the adsorption equilibrium and the simultaneous removal of surfactant molecules from the interface. By balancing the competitive kinetics between the two processes, we have prolonged the lifetime of the motion 40-fold. Our work presents an important advance in the query of long-lived self-propulsion transport through flexible interference at the molecular level and holds promise in electricity generation applications .

Interfacial Segregation in Oxide Scales on Nicrai-Based Alloys

1997 ◽  
Vol 3 (S2) ◽  
pp. 785-786
Author(s):  
K. Prüβner ◽  
K. B. Alexander ◽  
B. A. Pint ◽  
P. F. Tortorelli ◽  
I. G. Wright
Keyword(s):  
Cyclic Oxidation ◽  
Oxidation Behaviour ◽  
Reactive Elements ◽  
Oxide Scales ◽  
Protective Oxide ◽  
Form Complex ◽  
Scale Adhesion ◽  
Alumina Formers ◽  
Interfacial Segregation ◽  
Nicral Alloys

Previous studies addressing the segregation of reactive elements in protective oxide scales and their beneficial effect on scale adhesion have primarily concentrated on primary alumina-formers (e.g. β-NiAl + FeCrAl).In our study the oxidation behaviour of three NiCrAl alloys, which form complex scales was studied in air at 1423 K and at 1473 K, both in isothermal (100 h) and in cyclic oxidation (100 x lh). The composition (in at.-%) of these alloys is the following: General Electric alloy René N5 (64.9 Ni, 7.8 Cr, 13.9 Al, 0.1 Fe, 2.1 Ta, 0.05 Hf, 1.6 W, 1.0 Re, 0.15 Si, 7.3 Co, 0.9 Mo, 0.003 Y, 0.003 Zr, 4 ppm S, 0.25 C), Ni-7Cr-6.5Al+Y (80.1 Ni, 7.2 Cr, 12.5 Al, 0.01 Fe, 0.14 Si, 0.012 Y, 18 ppm S, 0.05 C) and Ni-10Cr-10Al+Y (71.2 Ni, 9.9 Cr, 18.8 Al, 0.01 Fe, 0.02 Si, 0.041 Y, 16 ppm S, 0.04 C).

On cusped interfaces

1998 ◽  
Vol 359 ◽  
pp. 313-328 ◽  
Author(s):  
YULII D. SHIKHMURZAEV
Keyword(s):  
Surface Tension ◽  
Free Surface ◽  
Reynolds Numbers ◽  
Present Theory ◽  
Similar Process ◽  
Surface Tension Gradient ◽  
Low Reynolds Numbers ◽  
Moving Contact Line ◽  
Moving Contact ◽  
Rate Of Dissipation

An asymptotic analysis of two-dimensional free-surface cusps associated with flows at low Reynolds numbers is presented on the basis of a model which, in agreement with direct experimental observations, considers this phenomenon as a particular case of an interface formation–disappearance process. The model was derived from first principles and earlier applied to another similar process: the moving contact-line problem. As is shown, the capillary force acting on a cusp from the free surface, which in the classical approach can be balanced by viscous stresses only if the associated rate of dissipation of energy is infinite, in the present theory is always balanced by the force from the surface-tension-relaxation ‘tail’, which stretches from the cusp towards the interior of the fluid. The flow field near the cusp is shown to be regular, and the surface-tension gradient in the vicinity of the cusp, caused and maintained by the external flow, induces and is balanced by the shear stress. Existing approaches to the free-surface cusp description and some relevant experimental aspects of the problem are discussed.

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