Improvement in the Oxidation Resistance of β-SiAlON Ceramics Produced from Mechanically Milled Powders

2012 ◽  
Vol 18-19 ◽  
pp. 281-290
Author(s):  
Onur Eser ◽  
S. Kurama
Keyword(s):  
Oxidation Resistance ◽  
High Temperature Oxidation ◽  
Oxidation Behavior ◽  
Oxidation Process ◽  
Isothermal Oxidation ◽  
High Energy ◽  
Particle Sizes ◽  
Temperature Oxidation ◽  
Dry Air ◽  
Milled Powders

In the present study the oxidation behavior of β-SiAlON ceramics, which were produced from conventional and high energy mechanical milled powders, was investigated. High energy mechanically milled powders have lower particle sizes ( 130 nm) than those of conventional powders (216 nm) and fully densified at lower temperatures with less amount of additives. The amount of additive is an important parameter to improve the high temperature oxidation resistance of SiAlON ceramics. The cyclic and isothermal oxidation tests were carried out at 1300 and 1400°C in dry air environment. The weight gain of oxidized samples was measured during the oxidation process. The alteration of oxide layer was analyzed by XRD and SEM. The results indicate that oxidation resistance of the samples produced from mechanically milled powders with less amount of additive is higher than that of conventional one. Therefore, β-SiAlON ceramics which were sintered at 100°C lower temperatures with less amount of additive (3.5 wt. % Y2O3), showed a better oxidation resistance.

Properties of Sputtered NiCrAlY Used for Protective Gun Tube Coatings

2011 ◽  
Vol 686 ◽  
pp. 613-617
Author(s):  
Jian Zhang ◽  
Cean Guo ◽  
Gang Zhang ◽  
Chong Rui Wang ◽  
Shi Ming Hao
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
High Temperature Oxidation ◽  
Oxidation Process ◽  
Complex Oxide ◽  
Isothermal Oxidation ◽  
Temperature Oxidation ◽  
Steel Balls ◽  
Steel Substrates ◽  
Micro Indentation

NiCrAlY coatings were deposited on CrNi3MoVA steel substrates by means of magnetron sputtering. The coatings were characterized in terms of their microstructure, hardness, friction coefficient, high-temperature oxidation resistance. Micro-indentation and tribometer testers were employed to measure the mechanical properties of NiCrAlY coatings and CrNi3MoVA steel. The results showed that the hardness of the coatings ranged from 5.7 to 5.9 GPa, with a higher value than that of CrNi3MoVA steel(4.1-4.3 GPa). The coefficient of steady-state friction of the coatings against 45-carbon-steel balls ranged from 0.35 to 0.40, with a lower value than that of CrNi3MoVA steel(0.63-0.68). The isothermal oxidation behavior at 850°C of the coatings were studied in comparison with CrNi3MoVA steel substrates. The results indicated that NiCrAlY coatings substantially increase the high-temperature oxidation resistance of CrNi3MoVA steel and the oxidation process was retarded mainly by the presence of outer complex oxide scales and a continuous Al2O3 inner layer on the coating.

Hot Corrosion Behavior of NiCoCrAlYSiHf Coating Deposited by Arc Ion Plating

2012 ◽  
Vol 472-475 ◽  
pp. 395-399
Author(s):  
Jia Hui Qu ◽  
Cean Guo ◽  
Jian Zhang
Keyword(s):  
High Temperature ◽  
Hot Corrosion ◽  
High Temperature Oxidation ◽  
Oxidation Behavior ◽  
Oxidation Process ◽  
Isothermal Oxidation ◽  
Temperature Oxidation ◽  
Arc Ion Plating ◽  
Ion Plating ◽  
Α Al2o3

Abstract: NiCoCrAlYSiHf coatings have been prepared by arc ion plating (AIP) on CrNi3MoVA steel ,which their microstructure and isothermal oxidation behavior at 950°C studied using SRD,SEM and EDAX. The results indicate that NiCoCrAlYSiHf coatings substantially increase the high-temperature oxidation resistance of CrNi3MoVA steel and the oxidation process was retarded mainly by the presence of α-Al2O3 oxide scale on the coating. Meanwhile, the major diffusion occured between the substrate element Fe and the coating element Co while Cr mainly distributed in the coating.

SiC/SiO2 Coating on Matrix Graphite Spheres of HTR Fuel Element Produced by a Two-Step Pack Cementation/High-Temperature Oxidation Process

2016 ◽  
Vol 852 ◽  
pp. 952-958 ◽  
Author(s):  
Ping Zhou ◽  
Zi Qiang Li ◽  
Hong Sheng Zhao ◽  
Kai Hong Zhang ◽  
Xiao Xue Liu ◽  
...  
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
High Temperature Oxidation ◽  
Oxidation Process ◽  
Reactor Core ◽  
Isothermal Oxidation ◽  
Pack Cementation ◽  
Temperature Oxidation ◽  
Matrix Graphite ◽  
Fuel Elements

Graphite is one of the most important material for the reactor core and fuel elements of high temperature gas-cooled reactor (HTR). Improving the oxidation resistance of graphite is very essential for the research of new fuel elements and the development of HTR. In this study, a gradient SiC layer of 500~700 μm was prepared on matrix graphite spheres by a two-step pack cementation, and the outer SiO2 layer prepared by the high-temperature oxidation process. The phases, microstructure, bonding strength and oxidation resistance of SiC/SiO2 coated matrix graphite spheres were investigated. The SiC/SiO2 coated matrix graphite spheres were carried on rapid thermal shocking tests from 1773 K to room temperature for 50 times without any cracks. The SiC/SiO2 coated matrix graphite spheres exhibits excellent anti-oxidation properties. No obvious weight loss was found after isothermal oxidation in air at 1273 K for 50 h and the weight gain was less than 1% at 1773 K in air for 50 h due to the oxidation of SiC layer.

Effect of 10 at.% Nb Addition on Sintering and High Temperature Oxidation of W0.5Cr0.5 Alloy

2012 ◽  
Vol 710 ◽  
pp. 308-313 ◽  
Author(s):  
Suresh Telu ◽  
Vaduganathan Karthik ◽  
Rahul Mitra ◽  
Shyamal Kumar Pabi
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
High Temperature Oxidation ◽  
Isothermal Oxidation ◽  
High Energy ◽  
Temperature Oxidation ◽  
Sinter Densification ◽  
High Temperature Oxidation Behavior ◽  
Nb Addition

The effect of 10 at.% Nb on the sintering and high temperature oxidation behavior of W0.5Cr0.5alloy was investigated. Elemental powder blends were made nanostructured by high energy mechanical milling, compacted and finally sintered under reduced atmosphere at 1790°C. The sintered samples were subjected to cyclic isothermal oxidation tests at 800°C to 1200°C in air. The experimental results shows superior sinterability and oxidation protection of W0.5Cr0.5alloy compared to pure W. Characterization of the oxide scales shows porous external W-rich oxide (WO3) formation which is not ideally suitable for oxidation resistance. On the other hand, W-Cr alloy with 10 at.% Nb shows the remarkable sinter densification (~98%) and oxidation resistance up to 1200°C. The oxide scale of the ternary alloy shows formation of stable Cr2O3, Nb2O5oxides and/or complex Cr-Nb oxide (CrNbO4), and there was no evidence of WO3formation in this case.

Oxidation behavior of bulk Ti3SiC2 at intermediate temperatures in dry air

2006 ◽  
Vol 21 (2) ◽  
pp. 402-408 ◽  
Author(s):  
H.B. Zhang ◽  
Y.C. Zhou ◽  
Y.W. Bao ◽  
J.Y. Wang
Keyword(s):  
Phase Transformation ◽  
Low Temperatures ◽  
Driving Force ◽  
Oxidation Behavior ◽  
Isothermal Oxidation ◽  
Oxide Scales ◽  
Temperature Oxidation ◽  
Dry Air ◽  
High Oxidation ◽  
Anomalous Oxidation

The isothermal oxidation behavior of bulk Ti3SiC2 at intermediate temperatures from 500 to 900 °C in flowing dry air was investigated. An anomalous oxidation with higher kinetics at lower temperatures was observed. This phenomenon resulted from the formation of microcracks in the oxide scales at low temperatures. The generation of these microcracks was caused by a phase change in the oxide products, i.e., the transformation of anatase TiO2 to rutile TiO2. This phase transformation resulted in tensile stress, which provided the driving force for the formation of the microcracks during oxidation. Despite the existence of microcracks, the intermediate-temperature oxidation of Ti3SiC2 generally obeyed the parabolic rate law and did not exhibit catastrophic destruction due to the fact that cracks occurring in the oxide layers were partially filled with amorphous SiO2. Therefore, further high oxidation kinetics was prevented.

Formation of discontinuous Al2O3 layers during high-temperature oxidation of RuAl alloys

2006 ◽  
Vol 21 (1) ◽  
pp. 276-286 ◽  
Author(s):  
P.J. Bellina ◽  
A. Catanoiu ◽  
F.M. Morales ◽  
M. Rühle
Keyword(s):  
High Temperature Oxidation ◽  
Oxidation Behavior ◽  
Microstructural Characterization ◽  
Isothermal Oxidation ◽  
Thermal Barrier ◽  
Interface Instability ◽  
Temperature Oxidation ◽  
Bond Coats ◽  
Barrier Coating ◽  
Transmission Electron

Bond coats play a crucial role in the performance of thermal barrier coating systems. Ru alloys have been identified as promising candidates; therefore, systematic studies were performed on the oxidation behavior of bulk RuAl (50–50 at.%). Isothermal oxidation and thermogravimetric analyses were performed at 1100 °C for different times ranging from 0.1 h to 500 h. Microstructural characterization was performed by scanning and transmission electron microscopy. The results showed the formation of an α–Al2O3 layer on top of a δ–Ru layer. Interface instability between these layers and evaporation of gaseous Ru-oxides lead to the formation of large elongated cavities and alternating α–Al2O3/δ–Ru layers.

High Temperature Oxidation Behavior of APM and APMT under Dry Air/Steam Condition

MRS Advances ◽  
2016 ◽  
Vol 1 (35) ◽  
pp. 2471-2476 ◽  
Author(s):  
KkochNim Oh ◽  
KwangSup Eom ◽  
Zhiyuan Liang ◽  
Preet M. Singh
Keyword(s):  
Stainless Steel ◽  
High Temperature ◽  
Thermogravimetric Analysis ◽  
Stainless Steels ◽  
High Temperature Oxidation ◽  
Oxidation Behavior ◽  
Fuel Cladding ◽  
Temperature Oxidation ◽  
Dry Air ◽  
High Temperature Oxidation Behavior

ABSTRACTOxidation behavior of alumina forming ferritic stainless steel (FeCrAl type stainless steels) grades APM and APMT, which are candidate alloys for fuel cladding, was studied using thermogravimetric analysis under dry air condition, and compared to that of ZIRLO®. In addition to the dry air condition, we also studied the high temperature oxidation behavior of APM and APMT under 100% steam condition in order to compare the effect of environment on the oxidation behavior of these alloys. APM and APMT showed an excellent oxidation resistance at high temperatures compared to ZIRLO® under dry air condition due to a stable Al2O3 oxide scale formed at the surface. Under steam condition, the oxidation rate of APM and APMT was found to be higher compared to that under the dry air condition.

Phase Constitution and Oxidation Resistance of B2 (Ir, Co)Al

2002 ◽  
Vol 753 ◽  
Author(s):  
Hideki Hosoda ◽  
Hiroshi Noma ◽  
Kenji Wakashima
Keyword(s):  
Oxidation Resistance ◽  
Oxidation Behavior ◽  
Hot Forging ◽  
Isothermal Oxidation ◽  
Oxidation Products ◽  
Phase Constitution ◽  
Temperature Oxidation ◽  
Arc Melting ◽  
Oxidation Resistant ◽  
Ultrahigh Temperature

ABSTRACTB2 iridium aluminide (IrAl) is hopeful for use as an ultrahigh temperature oxidation resistant coating above 1600K. In this study, the effect of Co substitution for Ir on phase constitution, hardness and oxidation behavior was studied for IrAl alloys. Alloys of (Ir, Co)-50mol%Al with various Co contents were fabricated by Ar-arc melting followed by hot-forging at 1773K. Oxidation behavior was evaluated using thermogravimetry (TG) in Ar-67%O2 up to 1823K. XRD and SEM were also carried out for alloy characterization. It was found that a continuous B2 solid solution (Ir,Co)Al is formed between IrAl and CoAl. Depending on the Co concentration, the oxidation products identified after heating to 1873K in Ar-67%O2 were Ir, IrO2 and A2O3 and/or Co2AlO4. Thin and continuous Al2O3 layers were observed after isothermal oxidation at 1673K when Co content is more than 20mol%Co. In this case, the weight change by isothermal oxidation at 1673K becomes higher with decreasing Co content. The (Ir,Co)Al alloys containing 20–40mol%Co exhibit higher oxidation resistance than CoAl and IrAl, and thus oxidation resistance of CoAl is improved by Ir addition.

Effect of Yttrium Addition on High Temperature Oxidation Resistance of Co-10Cr-5Al Alloys

2011 ◽  
Vol 391-392 ◽  
pp. 606-610 ◽  
Author(s):  
Huai Shu Zhang ◽  
Hong Hua Zhang ◽  
Jun Huai Xiang ◽  
Shan Wang ◽  
Di Wu
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
Oxidation Rate ◽  
High Temperature Oxidation ◽  
Oxidation Behavior ◽  
Temperature Oxidation ◽  
Linear Rate ◽  
Rate Law ◽  
Yttrium Addition ◽  
Parabolic Rate

The oxidation behavior of Co-10Cr-5Al-0.3Y alloy in 1 atm of pure O2 at 700°C was investigated. The addition of 0.3 at.%Y significantly increased the oxidation rate of the alloy and changed the oxidation behavior from the approximate parabolic rate law to linear rate law. The scale grown on the surface at 700°C was porous with many small voids and cracks, and was composed of an outer CoO layer and an inner complex layer rich in Al2O3 and Cr2O3 which were intermingled with yttric oxide and spinel Co(Cr, Al)2O4.

A STUDY OF NANOCOMPOSITE COATINGS ON THE SURFACE OF SHIP EXHAUST PIPE

2017 ◽  
Vol 24 (08) ◽  
pp. 1750112
Author(s):  
YAN SHEN ◽  
PRASANTA K. SAHOO ◽  
YIPENG PAN
Keyword(s):  
Oxidation Resistance ◽  
High Temperature Oxidation ◽  
Oxidation Behavior ◽  
Structural Characteristics ◽  
Composite Coatings ◽  
Nanocomposite Coatings ◽  
Pulsed Current ◽  
Exhaust Pipe ◽  
Temperature Oxidation ◽  
Better Than

In order to improve the high temperature oxidation resistance of exhaust pipes, the nanocomposite coatings are carried out on the surface of exhaust pipe by pulsed current electrodeposition technology, and the microstructure and oxidation behavior of the nanocomposite coatings are investigated experimentally. This paper mainly focuses on the experimental work to determine the structural characteristics and oxidation resistance of nanocomposite coatings in presence of attapulgite and cerium oxide CeO2. The results show that the amount of the attapulgite-CeO2 has significant influence on the structural properties of nanocomposite coatings. The surface of coating becomes more compact and smooth with the increase of the amount of the attapulgite and CeO2. Furthermore, the anti-oxidation performances of the nanocomposite coatings formed with attapulgite and CeO2 were both better than those of the composite coatings formed without attapulgite and CeO2.

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