Failure Mechanism of Crack on Oxide–Alloy Interface: An Elastic–Plastic Analysis

2011 ◽  
Vol 21 (5) ◽  
pp. 755-780 ◽  
Author(s):  
Honggang Zhou ◽  
Mohammed Cherkaoui
Keyword(s):  
High Temperature ◽  
Oxidation Process ◽  
Interfacial Crack ◽  
Ion Diffusion ◽  
Temperature Oxidation ◽  
Stress Diffusion ◽  
Interfacial Defects ◽  
Temperature Environment ◽  
Force Reduction ◽  
Substrate Alloy

Spallation failure of oxide scale in high-temperature environment, usually occurring at the oxide–alloy interface, primarily originates from the interfacial defects such as cracks. At the same time, the substrate alloy usually experience plastic deformation during high-temperature oxidation process. In this study, we extend our previous work on stress-diffusion interaction in the oxidation of Fe–Cr alloys by including the inelastic deformation of alloys and use it to study the growth mechanism of a crack lying along oxide–alloy interface. The results predict that the plasticity of alloy helps to prevent the crack from growing. It is also found that faster diffusion of species will lead to higher level of interfacial failure driving force. Reduction of Cr ion diffusion in oxide by introduction of the reactive element in the alloy will help to prevent interfacial crack growth.

INFLUENCE OF THE CROSSLINK STRUCTURE ON THE ACTIVATION ENERGY CALCULATED UNDER THERMO-OXIDATIVE CONDITIONS

2018 ◽  
Vol 91 (1) ◽  
pp. 205-224 ◽  
Author(s):  
Richard J. Pazur ◽  
T. Mengistu
Keyword(s):  
Activation Energy ◽  
Zinc Oxide ◽  
High Temperature ◽  
Oxidation Process ◽  
Activation Energies ◽  
Structure Stability ◽  
Temperature Oxidation ◽  
Network Chain ◽  
Temperature Activation ◽  
Sulfur Donor

ABSTRACT A series of six carbon black reinforced brominated poly(isobutylene-co-isoprene) (BIIR) compounds has been developed varying only in cure system type: sulfur, sulfur donor, zinc oxide, peroxide, phenolic resin, and ionic. Compounds were aged from room temperature up to 115 °C, and hardness, mechanical properties, and network chain density were measured. Non-Arrhenius behavior was observed due to data curvature from 70 to 85 °C. The oxidation process was adequately described by assigning low (23–85 °C) and high (85–115 °C) temperature regimes. Heterogeneous aging due to diffusion limited oxygen (DLO) occurred for heat aging above 85 °C, and all measured responses except tensile strength were strongly affected, causing lower activation energies. The activation energy for the high temperature oxidation process is in the range of 107 to 133 kJ/mol in the following ascending order: zinc oxide, ionic, sulfur donor, sulfur, peroxide, and resin. The midpoint of the high temperature activation energies is of the same order as the BIIR and poly(isobutylene) elastomers. The low temperature activation energy is in the range of 55–60 kJ/mol and is likely due to a combination of oxidative chain scission (crosslink density loss) and crosslinking recombination (network building) reactions. Apart from the crosslink structure stability, the presence of unsaturation along the polymer chain after vulcanization affects the high temperature activation energy.

High-temperature oxidation process of intermetallic compound Ti-42 at% Al

1993 ◽  
Vol 28 (4) ◽  
pp. 1067-1073 ◽  
Author(s):  
Akito Takasaki ◽  
Kozo Ojima ◽  
Youji Taneda ◽  
Taiji Hoshiya ◽  
Akira Mitsuhashi
Keyword(s):  
High Temperature ◽  
Intermetallic Compound ◽  
High Temperature Oxidation ◽  
Oxidation Process ◽  
Temperature Oxidation

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.

scholarly journals Oxidation and Characterization of Low Concentration Gas in High-Temperature Reactor

2020 ◽  
Author(s):  
Jinhua Chen ◽  
Guangcai Wen ◽  
Song Yan ◽  
Xiangyun Lan ◽  
Lu Xiao
Keyword(s):  
High Temperature ◽  
High Temperature Oxidation ◽  
Air Pressure ◽  
Oxidation Products ◽  
Heating Process ◽  
Temperature Oxidation ◽  
Low Concentration ◽  
Temperature Environment ◽  
Explosion Limit ◽  
High Temperature Environment

To achieve efficient utilization of low-concentration mine gas, reduce resource waste, and alleviate environmental pollution, high-temperature oxidation of low-concentration gas at a concentration range of 1.00% to 1.50% that is directly discharged into the atmosphere during coal mine production was oxidized to recover heat for reuse. The gas oxidation equipment was improved for the heating process, and the safety of low-concentration gas oxidation under high-temperature environment was evaluated. Experimental results showed that the reactor could provide a 1000 ℃ high-temperature oxidation environment for gas oxidation after installing high-temperature resistant ceramics. The pressure variation curves of the reactor with air and different concentrations of gas were similar. Due to the thermal expansion, the air pressure slightly increased and then returned to normal pressure. In contrast, the low-concentration gas exhibited a stable pressure response in the high-temperature environment of 1000 ℃. The outlet pressure was significantly greater than the inlet pressure, and the pressure difference between the inlet and outlet exhibited a trend to increase with the gas concentration. The explosion limit varied with the temperature and the blend with oxidation products. The ratio of measured gas pressure to air pressure after oxidation was below the explosion criterion, indicating that the measured concentration gas is still safe after the shift of explosion limit, which provides a safe concentration range for efficient use of low-concentration gas in the future.

A THERMO-DAMAGE STRENGTH MODEL FOR THE SiC-DEPLETED LAYER OF ULTRA-HIGH-TEMPERATURE CERAMICS ON HIGH TEMPERATURE OXIDATION

2013 ◽  
Vol 05 (03) ◽  
pp. 1350026 ◽  
Author(s):  
RUZHUAN WANG ◽  
WEIGUO LI ◽  
DAINING FANG
Keyword(s):  
High Temperature ◽  
High Temperatures ◽  
Fracture Strength ◽  
High Temperature Oxidation ◽  
Oxidation Process ◽  
High Porosity ◽  
Strength Model ◽  
Temperature Oxidation ◽  
Ultra High Temperature Ceramics ◽  
Ultra High Temperature

At high temperatures above 1650°C, the SiC -depleted layer of ultra-high-temperature ceramics which has high porosity appears during the oxidation process. In this present paper, based on the studies of the oxidative mechanisms and the fracture mechanisms of ultra-high-temperature ceramics under normal and high temperatures, a thermo-damage strength model for the SiC -depleted layer on high temperature oxidation was proposed. Using the model, the phase transformation, microstructure development and fracture performance in the SiC -depleted layer on high temperature oxidation were studied in detail. The study showed that the porosity is mainly related to the oxidation of SiC . And while the SiC is substantially completely oxidized, only a very small part of matrix is oxidized. The fracture strength of the SiC -depleted layer degrades seriously during the high temperature oxidation process. And the bigger the initial volume fraction of SiC , the lower the fracture strength of the SiC -depleted layer is. This layer may become the origin of failure of material, thus the further researches should be undertaken to improve the oxidation behavior for the ultra-high-temperature ceramics in a wider temperature range.

High Temperature X-Ray Diffraction Study of the Effect of Nb and Si on Oxidation behavior of Ti3Al Alloy

1994 ◽  
Vol 364 ◽  
Author(s):  
Guohua Qiu ◽  
Jiansheng Wu ◽  
Lanting Zhang ◽  
Dongliang Lin
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
Oxidation Process ◽  
Favorable Effect ◽  
Al Alloy ◽  
X Ray Diffraction ◽  
Temperature Oxidation ◽  
X Ray ◽  
Nb Addition

AbstractA disadvantage to the application of Ti3Al is its poor high temperature oxidation resistance. It is found that the element Nb or(and) Si can greatly reduce the oxidation rate of Ti3A1. A hot stage in situ X-ray diffractometer was used to determine the formation sequence of the oxide layers. At 800°C, TiO2 as well as Al2O3 was detected on the surface of binary Ti3Al at the beginning of the oxidation process. The addition of 5 at % Si to Ti3Al alloy did not favor the formation of an A12O3 layer. On the contrary, it inhibited the onset of Al2O3 to nearly 20 hours from the start of the oxidation process at the temperature of 800°C. The Nb addition also did not promote the formation of Al2O3. TiO2 formed first on the surface of Ti3Al-11 at % Nb alloy while TiN and TiAl formed consequently. Al2O3 was further delayed to 20 hours from the beginning of the oxidation process. When the Nb addition increased to 15 at %, however, TiN and TiAl were not found. It is suggested that the favorable effect of Nb and Si to the oxidation resistance of Ti3Al alloy is not due to their promotion of A12O3 layer, but probably due to some other mechanisms, such as the formation of TiN which serves as a diffusion barrier and decreases porosity in the TiO2 layer.

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