Modelling and Experiments Concerning Dendrite Re-Melting and Its Role in Microstructural Evolution in Spray Formed Ni Superalloys

2010 ◽  
Vol 654-656 ◽  
pp. 1363-1366 ◽  
Author(s):  
Yong Zhang ◽  
Z. Guo ◽  
Guo Qing Zhang ◽  
Jia Wei Mi ◽  
Patrick S. Grant
Keyword(s):  
Thermal Shock ◽  
Microstructural Evolution ◽  
Large Diameter ◽  
Liquid Mixtures ◽  
Spray Forming ◽  
Solid Particles ◽  
Fragmentation Behavior ◽  
Dendrite Fragmentation ◽  
Modelling Studies ◽  
Gleeble 3500

This paper presents a combined experimental and modelling approach to understand dendrite fragmentation of atomised metal alloy droplets during deposition in spray forming, and to study quantitatively the relationship between this dendrite fragmentation behavior and subsequent microstructural evolution. A Gleeble 3500 physical simulator was used to create controlled thermal shock conditions in solid-liquid mixtures of Ni superalloy IN718 atomised powders, which simulated the environment of droplet deposition during the twin-atomiser spray forming of large diameter IN718 alloy billets at BIAM. The experiments were complemented by phase field modelling studies at Oxford. Experiment and modelling supported the hypothesis that the characteristic equiaxed spray formed microstructure depends critically upon the rapid remelting and thermal shock of fine-scale dendrites in solid particles in the spray to provide a high density of embryonic grains.

Microstructural evolution during reactive spray forming of dispersion strengthened Cu alloy

1999 ◽  
Vol 5 (2) ◽  
pp. 141-147 ◽  
Author(s):  
Jongsang Lee ◽  
Eon-Sik Lee ◽  
W. J. Park ◽  
J. Y. Jung ◽  
S. Ahn ◽  
...  
Keyword(s):  
Microstructural Evolution ◽  
Spray Forming ◽  
Cu Alloy

Understanding and Mitigating Under-Deposit Corrosion in Large Diameter Crude Oil Pipelines: A Progress Report

2008 ◽  
Author(s):  
T. D. Place ◽  
Michael R. Holm ◽  
Colin Cathrea ◽  
Tom Ignacz
Keyword(s):  
Bacterial Species ◽  
Large Diameter ◽  
Progress Report ◽  
Solid Particles ◽  
Test Method ◽  
Internal Corrosion ◽  
Factors Affecting ◽  
Transmission Pipeline ◽  
Emulsified Water ◽  
Batch Treatment

This paper is an exploration of factors affecting internal corrosion of transmission pipeline systems (<0.5% S&W), as well as a progress report on research aimed at improving chemical mitigation of this threat in heavy oil product streams. Typical pipeline corrodents and corrodent transport mechanisms are explored. Transmission quality hydrocarbon products are shown to carry micro-emulsified water, various solid particles, solid particles with micro-attached water, and bacteria. While micro-emulsified water can be considered benign owing its ability to be transported harmlessly without accumulation; water-wetted solid particles have sufficient density to reach the pipe floor. Patterns of internal corrosion on a transmission pipeline are used to demonstrate the significance of solids accumulation leading to under-deposit corrosion. Analysis of pipeline sludge reveals significant populations of different bacterial species indicating the existence of a robust biomass capable of creating or sustaining a corrosive environment. Corrosivity testing of pipeline sludges was performed using two static autoclave coupon methods. One test method demonstrated that the addition of chemical inhibitor directly to the pipeline sludge could reduce corrosion rates as effectively as batch treatment of a clean coupon. A rotating mechanical contactor was designed and built to facilitate the blending of corrosion inhibitor with pipeline sludge under ‘like-pipe’ flow conditions, but results of sludge corrosivity testing using this device are not yet available.

A Combined CFD-Mechanistic Approach for Predicting Solid Particle Erosion in Annular Flow in Pipe Fittings and Elbows

2020 ◽  
Author(s):  
Farzin Darihaki ◽  
Elham Fallah Shojaie ◽  
Jun Zhang ◽  
Siamack A. Shirazi
Keyword(s):  
Multiphase Flow ◽  
Solid Particle ◽  
Annular Flow ◽  
Large Diameter ◽  
Solid Particles ◽  
Wall Material ◽  
Solid Particle Erosion ◽  
Flow Conditions ◽  
Particle Erosion ◽  
Wide Range

Abstract In internal flows, solid particles carried by the fluid could damage pipelines and fittings. Particles that are entrained in the fluid can cross streamlines and transfer a part of their momentum to the internal surface by impacts and cause local wall material degradation. Over the past decades, a wide range of models is introduced to predict particle erosion which includes empirical models, mechanistic models, and CFD which is currently the state-of-art numerical approach to simulate the erosion process. Multiphase flow under annular flow conditions adds to the complexity of the model. Although with the current computational capabilities transient CFD models are effectively applicable, this type of transient multiphase approach is not practical yet for engineering prediction of erosion especially for the large diameter applications with huge computational domains. Therefore, the presented combined approach could be utilized to obtain erosion rates for large diameter cases. Thus, an approach combining CFD and mechanistic multiphase models characterizing annular flow is developed to predict solid particle erosion. Different factors including film thickness in pipes and fittings which are affecting erosion under gas-dominated multiphase flow conditions are investigated. The results from the current approach are compared to experimental data and transient CFD simulations for annular flow in elbows showing a very good agreement with both.

Semisolid Microstructural Evolution of Equal Channel Angular Extruded Mg-Al Alloy During Partial Remelting

2008 ◽  
Vol 141-143 ◽  
pp. 557-562 ◽  
Author(s):  
S.M. Liang ◽  
Rong Shi Chen ◽  
En Hou Han
Keyword(s):  
Solid Solution ◽  
Microstructural Evolution ◽  
Equal Channel Angular Extrusion ◽  
Isothermal Holding ◽  
Solution Treatment ◽  
Solid Particles ◽  
Al Alloy ◽  
Semisolid State ◽  
Effects Of Temperature ◽  
Spherical Grains

Using equal channel angular extrusion (ECAE) process, which combine the advantages of grain refinement and induced strain, for preparing semisolid billets is a relatively new Strain Induced Melt Activation(SIMA)method. This paper investigates the remelting and semisolid isothermal holding behavior of Mg-9Al alloy after ECAE processing at 350°C. It has been found that 2 passes ECAE-ed billets are qualified for obtaining spherical grains after remelting and isothermal holding treatment. Increasing the ECAE process from 2 passes to 8 passes has no further significant effects on the size and roundness of the solid particles at the semisolid state. The effects of temperature and isothermal holding time on microstructural evolution have also been investigated. In addition, the solid solution treatment before the ECAE processing affected greatly on microstructural evolution of the alloy during ECAE processing and thus the following remelting and isothermal holding behavior. The Mg17Al12 precipitates were uniformly decomposed from the saturated solid solution in the solutionized samples during ECAE processing. The coalescence of grains together with the self-blocking effect generated more entrapped liquid in the solutionized sample at semisolid state. Moreover, the solid particles of solutionized samples have bigger size and grow faster, which are detrimental to SSM processability.

Microstructural Evolution in Spray Forming

2017 ◽  
pp. 265-295
Author(s):  
Patrick S. Grant ◽  
Guilherme Zepon ◽  
Nils Ellendt ◽  
Volker Uhlenwinkel
Keyword(s):  
Microstructural Evolution ◽  
Spray Forming

Case History Fitness-for-Service Assessment of Cyclic Catalytic Reformer Motor Operated Valves in the Petrochemical Industry

2011 ◽  
Author(s):  
Nick A. Carr ◽  
Kraig S. Shipley ◽  
David J. Dewees
Keyword(s):  
Ambient Temperature ◽  
Thermal Shock ◽  
Case History ◽  
Petrochemical Industry ◽  
Large Diameter ◽  
Catalyst Regeneration ◽  
Process Flow ◽  
Valve Body ◽  
Catalytic Reformer

Reactors of cyclic catalytic reformers require catalyst regeneration about every 7 days (∼50 cycles per year). To facilitate the in situ regeneration, large diameter motor operated valves (MOV) are used (typically Class 600 NPS 8 to NPS 16 API 600 gate block valves). Double block-n-bleed arrangements of the MOVs are used to assure isolation of the 350 psig 960°F process and regeneration media. The regeneration MOVs will be closed and in isolation for up to 4 days and can reach temperatures close to ambient depending on their distance from the process flow. Once the MOVs are swung open, the valve body quickly transitions from ambient temperature to 960°F over a matter of minutes. Such an extreme thermal shock has historically led to a number of cracks in the MOV valve bodies. With each unit having over 50 MOVs, it becomes expensive and time consuming to open every MOV at a scheduled turnaround, inspect, and repair any cracking noticed.

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