Effects of Water Vapor on the Oxidation Behaviors of Cr-Al-N Coatings

2012 ◽  
Vol 476-478 ◽  
pp. 2083-2086
Author(s):  
Ming Zhu ◽  
Zhi Hua Wang
Keyword(s):  
Water Vapor ◽  
Aluminum Content ◽  
Reactive Magnetron ◽  
Oxide Scales ◽  
Dry Air ◽  
Oxidation Rates ◽  
Parabolic Law ◽  
Surface Morphologies ◽  
K38g Alloy ◽  
Oxidation Behaviors

Cr1-xAlxN coatings with different aluminum content were deposited on K38G alloy by reactive magnetron sputtering method. Oxidation behaviors of these coatings were investigated at 1000°C in air+10 vol.% water vapor. The surface morphologies and the microstructure of the oxide scales were analyzed by SEM and XRD, respectively. The results showed that the oxidation of the Cr1-xAlxN coatings in the wet air also obeyed the parabolic law; however, compared to that in the dry air, existing of 10 vol. % water vapor increased the parabolic rate constants of the coatings. It was believed that the accelerating of the oxidation rates was owing to easily outwards diffusion of Cr through the looser and coarser oxide scales formed on the surface of the coatings when oxidized in wet air.

scholarly journals The Cyclic Oxidation and Hardness Characteristics of Thermally Exposed Titanium Prepared by Inductive Sintering-Assisted Powder Metallurgy

Crystals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 104
Author(s):  
Fahamsyah H. Latief ◽  
El-Sayed M. Sherif ◽  
Agus S. Wismogroho ◽  
Wahyu B. Widayatno ◽  
Hany S. Abdo
Keyword(s):  
Powder Metallurgy ◽  
Single Phase ◽  
Oxide Scales ◽  
Cyclic Tests ◽  
X Ray Diffraction ◽  
X Ray ◽  
Oxidation Rates ◽  
Parabolic Law ◽  
Kinetics Of ◽  
Hardness Values

The oxidation and hardness of thermally exposed titanium (Ti) prepared using inductive sintering-assisted powder metallurgy was evaluated through cyclic tests in air at 700–900 °C for 100 h (5 cycles). In general, the oxidation kinetics of the Ti samples followed the parabolic law and their oxidation rates increased with increasing oxidation temperatures. The rutile form of titanium dioxide (TiO2) was detected by X-ray diffraction in the oxide scales after oxidation at 700 °C and 900 °C. Furthermore, the TiO2 grain size and thickness were significantly influenced by an increase in the oxidation temperature. Lastly, the formation of rutile as a single-phase on the surface of oxidized Ti enhanced the hardness of the oxide scales, whereas the substrate had lower hardness values than the oxide scales due to diffusion of Ti atoms at the surface to form the TiO2 oxide scales.

scholarly journals Scale Formation on HSLA Steel during Continuous Casting Part I: The Effect of Temperature–Time on Oxidation Kinetics

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1243 ◽  
Author(s):  
Rosa Maria Pineda Huitron ◽  
Pavel Ernesto Ramírez López ◽  
Esa Vuorinen ◽  
Pooria Nazen Jalali ◽  
Leonardo Pelcastre ◽  
...  
Keyword(s):  
Water Vapor ◽  
Continuous Casting ◽  
Oxide Scale ◽  
Surface Quality ◽  
Hsla Steel ◽  
Effect Of Temperature ◽  
Dry Air ◽  
Oxidation Rates ◽  
Steel Slabs

The findings in this work enhance the understanding of oxidation mechanisms and scale growth at high temperatures of a high strength low alloy (HSLA) steel for improving surface quality during continuous casting. The oxidation phenomenon was investigated under dry air and water vapor atmospheres by heating specimens at 1000, 1100, and 1200 °C at different holding times. Temperature and time had great effects on the kinetics, where faster (i.e., parabolic) oxidation rates were present under water vapor when compared with the dry air condition. Temperature strongly influenced the number of defects, such as pores, voids, gaps and micro-cracks, formed in the oxide scale. A phase analysis confirmed the presence of FeO as the first phase formed at the steel surface, Fe3O4 as the middle and thicker phase, and Fe2O3 as the last phase formed in the oxide/air interface. The micromechanics of the oxides demonstrated that a combination of phases with high (wüstite) and low plasticity (magnetite and hematite) could also have been the reason for the uneven cooling during Continuous Casting (CC) that resulted in the undesired surface quality of the steel slabs. This work gives a good look at the oxide scale effect on the surface quality of steel slabs through an understanding the kinetics during oxidation.

Evaluation on the High-Temperature Oxidation Behavior of HP Steam Turbine Rotor Materials

2013 ◽  
Vol 750-752 ◽  
pp. 420-425
Author(s):  
Li Bin Niu ◽  
Takuya Shibata
Keyword(s):  
High Temperature ◽  
Steam Turbine ◽  
High Temperature Oxidation ◽  
Turbine Rotor ◽  
Oxide Scales ◽  
Temperature Oxidation ◽  
Steam Turbine Rotor ◽  
Oxidation Rates ◽  
High Temperature Oxidation Behavior ◽  
Oxidation Behaviors

High-temperature oxidation behaviors of super-clean 9CrMoV steel and 1CrMoV steel for HP steam turbine rotor materials were investigated. The super-clean 9CrMoV steel showed a superior high-temperature oxidation resistance with very small oxidation rates even though at 630°C, because the oxidation was restrained by the Cr-oxides formed near the base metal. On the other hand, the oxide scales formed on the 1CrMoV steel were composed of Fe-oxides, and the oxidation rate increased remarkably at the temperatures above 610°C.

Difference oxidation behaviors of Ni8Al and Ni25Cr coatings in air with water vapor at 650∘

2021 ◽  
pp. 2150274
Author(s):  
Dingjun Li ◽  
Wenlang Huang ◽  
Xiaohu Yuan ◽  
Taihong Huang ◽  
Chao Li ◽  
...  
Keyword(s):  
Water Vapor ◽  
High Velocity ◽  
Cyclic Oxidation ◽  
Oxidation Behaviour ◽  
Fuel Spray ◽  
High Velocity Oxygen Fuel ◽  
Service Environment ◽  
Generator Unit ◽  
Oxygen Fuel ◽  
Oxidation Behaviors

The oxidation behaviour of Ni8Al and Ni25Cr coatings produced by high velocity oxygen fuel spray (HVOF) which were deposited on Fe-based alloys (CB2) was investigated. We simulated the service environment of the steam generator unit, and put the samples in a thermostatic tube furnace at 650[Formula: see text] in air with 20 wt.% water vapor for 1000 hours of cyclic oxidation. The formation mechanism are explained using SEM, XRD, and EDX. There were no spallations and obvious cracks in both coatings. Ni25Cr coating generated a better protection oxides scale than that scale on Ni8Al. The behavior and mechanism of the oxide scale formation had an important influence in coatings and we have discussed these phenomenons in the study.

Oxidation Characteristics of Vapor-Plated Tungsten

CORROSION ◽  
1966 ◽  
Vol 22 (10) ◽  
pp. 291-293 ◽  
Author(s):  
VERNON A. NIEBERLEIN
Keyword(s):  
Powder Metallurgy ◽  
Vapor Deposition ◽  
Oxidation Kinetics ◽  
Activation Energies ◽  
Humid Air ◽  
Dry Air ◽  
Oxidation Rates ◽  
Complex Shapes ◽  
Oxidation Characteristics

Abstract Vapor-deposition is being used increasingly for fabricating complex shapes from tungsten. In contrast to conventional tungsten whose oxidation kinetics have been well explored, vapor-deposited material has never been investigated systematically with regard to oxidation. Oxidation rates were run at 600–1000 C (1112–1832 F) in air using a recording balance. Activation energies were calculated and oxidation rates were compared to those of sheet tungsten prepared using powder metallurgy techniques. Humid air and dry air were compared as corroding media.

Silica Nanocomposite Membrane for Dehumidification

2017 ◽  
Author(s):  
Omar Almahmoud ◽  
Tae-Youl Choi ◽  
Young-Soo Seo ◽  
Hyo-Sun Kim ◽  
Kevin A. Johnson
Keyword(s):  
Water Vapor ◽  
Flow Rate ◽  
Driving Forces ◽  
Comsol Multiphysics ◽  
The Finite Element Method ◽  
Dry Air ◽  
Hydrophobic Polymer ◽  
Silica Nanocomposite ◽  
Novel Design ◽  
Polyurethane Membrane

Various designs of novel membrane (silica nanocomposite polyurethane membrane) were tested for its optimal configuration in a membrane-based dehumidification system. This membrane was designed with a hydrophobic polymer matrix with hydrophilic silica nanochains. In this dehumidification process, two driving forces were suggested: concentration gradient of water vapor in the atmospheric air channel due to sweep gas and pressure gradient due to vacuum. This paper describes validation of the model configurations using the finite element method software (COMSOL Multiphysics) with experiments. Pressurized air enters an air duct at 1–5 liters per minute flow rate. Air is then humidified using a misting nozzle until saturation. Then the humid air passes by the membrane with a vacuum pump connected vertically to the duct to maximize the dehumidification rate. A novel design showed water vapor reduction from 19.4 grams of water vapor per kilogram of dry air to 16.9 grams of water vapor per kilogram of dry air for the 1 liter per minute flow rate of the 47 mm diameter membrane.

scholarly journals The lightness of water vapor helps to stabilize tropical climate

2020 ◽  
Vol 6 (19) ◽  
pp. eaba1951 ◽  
Author(s):  
Seth D. Seidel ◽  
Da Yang
Keyword(s):  
Water Vapor ◽  
Longwave Radiation ◽  
Tropical Climate ◽  
Climate Feedback ◽  
Tropical Atmosphere ◽  
Radiative Effect ◽  
Buoyancy Effect ◽  
Moist Air ◽  
Dry Air ◽  
Earth’S Climate

Moist air is lighter than dry air at the same temperature, pressure, and volume because the molecular weight of water is less than that of dry air. We call this the vapor buoyancy effect. Although this effect is well documented, its impact on Earth’s climate has been overlooked. Here, we show that the lightness of water vapor helps to stabilize tropical climate by increasing the outgoing longwave radiation (OLR). In the tropical atmosphere, buoyancy is horizontally uniform. Then, the vapor buoyancy in the moist regions must be balanced by warmer temperatures in the dry regions of the tropical atmosphere. These higher temperatures increase tropical OLR. This radiative effect increases with warming, leading to a negative climate feedback. At a near present-day surface temperature, vapor buoyancy is responsible for a radiative effect of 1 W/m2 and a negative climate feedback of about 0.15 W/m2 per kelvin.

scholarly journals A model of HDO in the tropical tropopause layer

2003 ◽  
Vol 3 (6) ◽  
pp. 2173-2181 ◽  
Author(s):  
A. E. Dessler ◽  
S. C. Sherwood
Keyword(s):  
Water Vapor ◽  
Isotopic Composition ◽  
Vertical Profile ◽  
Tropical Tropopause Layer ◽  
Physical Constraints ◽  
Dry Air ◽  
Tropical Tropopause

Abstract. Any theory of water vapor in the tropical tropopause layer (TTL) must explain both the abundance and isotopic composition of water there. In previous papers, we presented a model of the TTL that simulated the abundance of water vapor as well as the details of the vertical profile. That model included the effects of "overshooting" convection, which injects dry air directly into the TTL. Here, we present results for the model after modifying it to include water's stable isotopologue HDO (where D represents deuterium, 2H). We find that the model predicts a nearly uniform HDO depletion throughout the TTL, in agreement with recent measurements. This occurs because the model dehydrates by dilution, which does not fractionate, instead of by condensation. Our model shows that this dehydration by dilution is consistent with other physical constraints on the system. We also show the key role that lofted ice plays in determining the abundance of HDO in the TTL. Such lofted ice requires a complementary source of dry air in the TTL; without that, the TTL will rapidly saturate and the lofted ice will not evaporate.

Effect of Cold Working and Annealing on Oxidation Rates of Copper in Dry Air at Room Temperature

CORROSION ◽  
1968 ◽  
Vol 24 (12) ◽  
pp. 407-410 ◽  
Author(s):  
P. K. KRISHNAMOORTHY ◽  
S. C SIRCAR
Keyword(s):  
Room Temperature ◽  
Lattice Distortion ◽  
Cold Working ◽  
Oxide Films ◽  
Dry Air ◽  
Oxidation Rates ◽  
Substrate Metal ◽  
Thin Oxide Films ◽  
Thin Oxide ◽  
Kinetics Of

Abstract The effect of plastic deformation and further annealing on the kinetics of growth of thin oxide films on copper at 30 C (86 F) has been investigated. Oxidation rate was found to decrease markedly with increasing deformation. Further annealing showed an increase in the rate, the most pronounced changes occurring during the recrystallization stage. Results are interpreted in the light of Cabrera-Mott theory of growth of very thin oxide films on metals. The change in rate has been related to the concentration of cation vacancies in the Cu2O semi-conductor, which is dependent on the lattice distortion and defect concentration of the substrate metal.

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