Evaluation of Nanocrystalline Coatings for Coal-Fired Ultrasupercritical Boiler Tubes

2010 ◽  
Vol 132 (6) ◽  
Author(s):  
N. S. Cheruvu ◽  
R. Wei ◽  
M. R. Govindaraju ◽  
D. W. Gandy
Keyword(s):  
Oxide Scale ◽  
Internal Oxidation ◽  
Cyclic Oxidation ◽  
Thermal Exposure ◽  
Grain Structure ◽  
Ultrafine Grain ◽  
Al2o3 Scale ◽  
Scale Spallation ◽  
Al Content ◽  
Ultrafine Grain Structure

Cyclic oxidation behavior and microstructural degradation of nanocrystalline Ni–20Cr–xAl (where x=4 wt %, 7 wt %, and 10 wt %) coatings have been investigated. The coatings were deposited on Haynes 230 samples using a magnetron sputtering technique. Cyclic oxidation tests were conducted on the uncoated and coated samples at peak temperatures of 750°C and 1010°C for up to 2070 thermal cycles between the peak and room temperatures. The results showed that a dense Al2O3 scale was formed on the external surface of all coatings after exposure at both temperatures. All three coatings showed no evidence of internal oxidation after exposure at 750°C. Among the three coatings, only the coating containing 4 wt % Al showed evidence of internal oxidation along the columnar grain boundaries after exposure at 1010°C. The Al2O3 scale exhibited good spallation resistance during cyclic oxidation tests at both temperatures. As the Al content in the coating increased from 4 wt % to 7 wt % or 10 wt %, thermal exposure led to precipitation of coarse Al-rich particles at the coating/substrate interface. In addition, thermal exposure at both temperatures led to rapid depletion of Al in the coating and grain coarsening of the coatings. The improvement in oxide scale spallation resistance and accelerated depletion of aluminum are attributed to the ultrafine grain structure of the coating and oxide scale.

Evaluation of Nanocrystalline Coatings for Coal-Fired Ultra-Supercritical Boiler Tubes

2009 ◽  
Author(s):  
N. Sastry Cheruvu ◽  
Ronghua Wei ◽  
Madhavrao Govindaraju ◽  
David W. Gandy
Keyword(s):  
Oxide Scale ◽  
Internal Oxidation ◽  
Cyclic Oxidation ◽  
Thermal Exposure ◽  
Grain Structure ◽  
Ultrafine Grain ◽  
Al2o3 Scale ◽  
Scale Spallation ◽  
Al Content ◽  
Ultrafine Grain Structure

Cyclic oxidation behavior and microstructural degradation of nanocrystalline Ni-20Cr-xAl (where x = 4, 7, and 10 wt.%) coatings have been investigated. The coatings were deposited on Haynes 230 samples using a magnetron sputtering technique. Cyclic oxidation tests were conducted on the coated and uncoated samples at peak temperatures of 750°C and 1010°C for up to 2070 thermal cycles between the peak and room temperatures. The results showed that a dense Al2O3 scale was formed on the external surface of all coatings after exposure at both temperatures. All three coatings showed no evidence of internal oxidation after exposure at 750°C. Among the three coatings, the coating containing 4 wt.% Al only showed evidence of internal oxidation along the columnar grain boundaries after exposure at 1010°C. The Al2O3 scale exhibited good spallation resistance during cyclic oxidation tests at both temperatures. As the Al content in the coating increased from 4 to 7 or 10 wt.%, thermal exposure led to precipitation of coarse Al-rich particles at the coating/substrate interface. In addition, thermal exposure at both temperatures led to rapid depletion of Al in the coating and grain coarsening of the coatings. The improvement in oxide scale spallation resistance and accelerated depletion of aluminum are attributed to the ultrafine grain structure of the coating and oxide scale.

Oxidation Behavior of Sputter Deposited Nanocrystalline and Conventional Plasma Sprayed MCrAl(Y) Coatings

2010 ◽  
Author(s):  
N. Sastry Cheruvu ◽  
Ronghua Wei ◽  
David W. Gandy
Keyword(s):  
Cyclic Oxidation ◽  
Grain Structure ◽  
Scale Spallation ◽  
Outward Diffusion ◽  
Al Content ◽  
Fine Grain ◽  
Plasma Sprayed Coatings ◽  
Sputter Deposited ◽  
Plasma Sprayed ◽  
Short Time

The MCrAl-type coatings with, or without, yttrium are widely used for oxidation and/or hot corrosion protection of hot section components of gas turbine engines. Recently, there has been great interest in developing nano or microcrystalline coatings since these coatings offer excellent oxidation and corrosion resistance compared to the conventional coatings. Cyclic oxidation and microstructral degradadation behavior of sputter deposited nanocrystalline Ni-20Cr-10Al coating has been investigated at 1010°C. The coating was deposited on Haynes 230 samples using a magnetron sputtering technique. This technique produced a coating with a grain size of ∼9 nm. The cyclic oxidation results showed that the sputter deposited Ni-20Cr-10Al coating exhibited better oxidation resistance in terms of weight loss kinetics compared to the conventional plasma-sprayed NiCoCrAlY and PWA 286 coatings. The Al content in the nanocrystalline coating was consumed in a relatively short time due to inward and outward diffusion of Al. The accelerated consumption of Al was presumably due to enhanced grain boundary diffusion resulting from the ultra-fine grain structure in the coating. Variation of oxide-scale spallation resistance during thermal cycling, internal oxidation of the coatings, and the rate of Al consumption due to inward and outward diffusion of Al between the nanocrystalline and plasma sprayed coatings is presented.

Grain Refinement and Deformation Behavior of Ultrafine Grained Pd and Pd-Ag Alloys Produced by HPT

2008 ◽  
Vol 584-586 ◽  
pp. 182-187
Author(s):  
Lilia Kurmanaeva ◽  
Yulia Ivanisenko ◽  
J. Markmann ◽  
Ruslan Valiev ◽  
Hans Jorg Fecht
Keyword(s):  
Mechanical Properties ◽  
Deformation Behavior ◽  
Materials Science ◽  
High Pressure Torsion ◽  
Uniform Elongation ◽  
Grain Structure ◽  
Coarse Grained ◽  
Ultrafine Grain ◽  
Ultrafine Grained ◽  
Ultrafine Grain Structure

Investigations of mechanical properties of nanocrystalline (nc) materials are still in interest of materials science, because they offer wide application as structural materials thanks to their outstanding mechanical properties. NC materials demonstrate superior hardness and strength as compared with their coarse grained counterparts, but very often they possess a limited ductility or show low uniform elongation due to poor strain hardening ability. Here, we present the results of investigation of the microstructure and mechanical properties of nc Pd and Pd-x%Ag (x=20, 60) alloys. The initially coarse grained Pd-x% Ag samples were processed by high pressure torsion, which resulted in formation of homogenous ultrafine grain structure. The increase of Ag contents led to the decrease of the resulted grain size and change in deformation behavior, because of decreasing of stacking fault energy (SFE). The samples with larger Ag contents demonstrated the higher values of hardness, yield stress and ultimate stress. Remarkably the uniform elongation had also increased with increase of strength.

Ultrafine Grain Structure Development in Aluminium Alloy by Strain Hardening using CCGP

2021 ◽  
Vol 1 (2) ◽  
pp. 25-31
Author(s):  
HS Siddesha ◽  
Suhaaskapardhi BS ◽  
Goutham C
Keyword(s):  
Tensile Strength ◽  
Aluminium Alloy ◽  
Research Work ◽  
Industrial Applications ◽  
Grain Structure ◽  
Ultrafine Grain ◽  
Fine Grained ◽  
Processed Material ◽  
Super Plastic ◽  
Ultrafine Grain Structure

Severe Plastic Deformation (SPD) processes are for developing ultrafine grained (UFG) structured materials for different Industrial applications. Cyclic Constrained Groove Pressing (CCGP) is a technique, produce fine grained structures in metallic sheets or plates in mass production. The objective of research work is to investigate the influence of CCGP processing on the super plastic behaviour of an Aluminium alloy. Samples in “ascast” materials processed by CCGP with as cast, 1, 2, 3 and 4 passes. Processed Material study for microhardness and Tensile strength mechanical properties test were done for different test specimens. Grain refinement, microhardness and Tensile strength increased with the number of CCGP passes.

Grain Refinement of an Al-Cu-Mg Alloy by Microalloying and Common Thermo-Mechanical Treatment

2007 ◽  
Vol 546-549 ◽  
pp. 917-922
Author(s):  
Bao Lin Wu ◽  
Gui Ying Sha ◽  
Yi Nong Wang ◽  
Yu Dong Zhang ◽  
Claude Esling
Keyword(s):  
Thermal Stability ◽  
High Temperature ◽  
Mechanical Treatment ◽  
Grain Structure ◽  
Mg Alloy ◽  
Ultrafine Grain ◽  
Fine Grain ◽  
Thermo Mechanical Treatment ◽  
Ultrafine Grain Structure ◽  
Thermal Stability Of

Heavy deformation plus micro alloying could be an effective way to obtain ultrafine grain structure of metals. In the present work, an Al-Cu-Mg alloy was microalloyed with Zr to obtain homogeneous precipitates and then heavily deformed by conventional forging at high temperature. The possible refining processing routes were studied and the superplasticity behaviors of the alloy was investigated. Results show that the micro alloyed alloy can be stably refined to 3-5μm under conventional processing routes. The Al-3Zr precipitates act both as additional sites to enhance recrystallization nucleation rate and pins to impede grain growth to increase the thermal stability of the fine grain structure. However, as the Al3Zr precipitates remains along grain boundaries, the superplastic capability of the material is not high. At 430°C with 1×10-4S-1 strain rate, the elongation obtained was 260%.

scholarly journals The Production of Material with Ultrafine Grain Structure in Al-Zn Alloy in the Process of Rapid Solidification

2014 ◽  
Vol 14 (2) ◽  
pp. 57-62
Author(s):  
M. Szymaneka ◽  
B. Augustyn ◽  
D. Kapinos ◽  
S. Boczkal ◽  
J. Nowak
Keyword(s):  
Rapid Solidification ◽  
Melt Spinning ◽  
Hot Extrusion ◽  
High Strength ◽  
Strength Properties ◽  
Grain Structure ◽  
Ultrafine Grain ◽  
Plastic Working ◽  
Metal Treatment ◽  
Ultrafine Grain Structure

Abstract In the aluminium alloy family, Al-Zn materials with non-standard chemical composition containing Mg and Cu are a new group of alloys, mainly owing to their high strength properties. Proper choice of alloying elements, and of the method of molten metal treatment and casting enable further shaping of the properties. One of the modern methods to produce materials with submicron structure is a method of Rapid Solidification. The ribbon cast in a melt spinning device is an intermediate product for further plastic working. Using the technique of Rapid Solidification it is not possible to directly produce a solid structural material of the required shape and length. Therefore, the ribbon of an ultrafine grain or nanometric structure must be subjected to the operations of fragmentation, compaction, consolidation and hot extrusion. In this article the authors focussed their attention on the technological aspect of the above mentioned process and described successive stages of the fabrication of an AlZn9Mg2.5Cu1.8 alloy of ultrafine grain structure designated for further plastic working, which enables making extruded rods or elements shaped by the die forging technology. Studies described in the article were performed under variable parameters determined experimentally in the course of the alloy manufacturing process, including casting by RS and subsequent fragmentation.

Ultrafine-grain structure and properties of carbon-steel wire after complex deformation

2014 ◽  
Vol 44 (5) ◽  
pp. 390-393 ◽  
Author(s):  
M. A. Polyakova ◽  
A. E. Gulin ◽  
O. A. Nikitenko ◽  
D. V. Konstantinov ◽  
M. S. Zherebtsov
Keyword(s):  
Carbon Steel ◽  
Steel Wire ◽  
Grain Structure ◽  
Ultrafine Grain ◽  
Structure And Properties ◽  
Complex Deformation ◽  
Ultrafine Grain Structure

Effect of Heat Treatment on the Mechanical Properties of Wrought Al-Zn-Mg-Cu Alloy Cast by Rapid Solidification

2013 ◽  
Vol 765 ◽  
pp. 496-500 ◽  
Author(s):  
Dawid Kapinos ◽  
Marcin Szymanek ◽  
Bogusław Augustyn ◽  
Maciej Gawlik
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Rapid Solidification ◽  
Solution Heat Treatment ◽  
Grain Structure ◽  
Ultrafine Grain ◽  
Cu Alloy ◽  
Optimum Heat ◽  
Ultrafine Grain Structure ◽  
Alloy Cast

The article presents the change in mechanical properties of AlZn9Mg2.5Cu1.8 alloy resulting from the process of solution heat treatment and aging. The heat treatment was performed on a unique UMSA (Universal Metallurgical Simulator and Analyzer) device. The aim of the study was to determine optimum heat treatment parameters for the tested alloy of ultrafine grain structure obtained by Rapid Solidification (RS). To achieve this purpose, heat treatment to the T4 and T6 condition was carried out. The solution heat treatment was carried out at a constant temperature of 460 °C for 2 hours, while the time - temperature parameters of the aging process varied. The treatment undertaken resulted in improved mechanical properties.

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