Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : oxidation

Neural NetworkModeling of Oxidation Kinetics in Air of Steel-T21 Alloy Coated by Simultaneous Germanium-Doped Aluminizing-Silicon zing Process

Abbas Khammas; Mohanned M. H.AL-Khafaji

Engineering and Technology Journal, 2013, Volume 31, Issue 4, Pages 632-645

In this work a pack cementation of germanium-doped aluminum and silicon coatings on low alloy steel type-T21 has been applied. This gives significant improvement in the oxidation. Steel-T21 was coated with germanium-doped aluminizing-siliconizing. Diffusion coating was carried out at 1050oC for 6 h under an Ar atmosphere by simultaneous germanium-doped aluminizing-siliconzing process. Cyclic oxidation tests were conducted on the coated steel-T21 alloy in the temperature range oxide 300-900oC in air for 102 h at 3 h cycle. The results showed that the oxidation kinetics for coated system in air can be represented by parabolic curve .Oxide phases that formed on coated system are SiO2 and Cr2O3. A neural network model of oxidation kinetics has been proposed to model the oxidation kinetic. The neural model shows good agreement with the experimental data.

Isothermal Oxidation of Simple and Pt-Modified Diffusion Coating on Inconel Alloy 600 In Water Vapor

Khalil; Al- Hatab; Al- Alqawie; Hussein; Ahmed Ali; Moosa

Engineering and Technology Journal, 2009, Volume 27, Issue 2, Pages 288-299

In this work the oxidation behavior of both inconel alloy 600 and coated system
(Pt-modified aluminide coating) was investigated in pure water vapor H2O in the
temperature range 700 - 900 ºC. The platinum was deposited by electrochemical
method. Pt-modified aluminide coating was applied to inconel alloy 600 by using singlestep
high activity pack cementation method. The weight gain measurements indicate
that the oxidation kinetic is parabolic for uncoated and coated alloy. At temperatures
below 900 ºC the inconel alloy 600 is less aggravated in water vapor environments
because it is a chromia former alloy. At 700 ºC, water vapor does not have a significant
effect on the spalling of oxide scales. At 900 ºC, water vapor causes spalling of the
oxide scales during isothermal oxidation of inconel alloy 600. Therefore, it is concluded
that this alloy should not be used above 900 ºC in water vapor environments. Large
voids were found at the oxide scales-substrate interface and at grains or at grain
boundaries due to the chromium outward diffusion toward the oxide scales.
At 900 ºC, the parabolic rate constant (kp) of the coated system was one order of
magnitude lower than that for the uncoated alloy. It was concluded that, water vapor
exhibit little effect on the Pt-modified aluminide coating. Oxide phases that formed on
coated system are: Al2O3, NiAl2O4, Cr2O3, and NiFe2O4.

Oxidation and Corrosion Mechanism of Steel Alloys and Inconel 600 Alloy in Liquid–Lead-Bismuth Eutectic

Ahmed Moosa

Engineering and Technology Journal, 2008, Volume 26, Issue 11, Pages 1369-1383

The alloys used in this study were two types pf stainless steels (304SS and
316 SS) , low alloy steel (Type T22-ASTM) and Inconel 600 alloy `(nickelbase
superalloy). The oxidation mechanism were studied for three steel
alloys and for inconel 600 in liquid Pb-Bi eutectic (LBE) in the temperature
range 450- 550 oC using stagnant test . A model based on the experiments
of Cr oxidation at high temperature with scale vaporization was applied to
the present oxidation process by replacing the vaporization rate with the
mass-transfer-corrosion rate. The results indicate that all steel alloys
showed an oxidation/corrosion behavior. The oxidation kinetics is parabolic
and the corrosion kinetics is linear. The parabolic oxidation rate constant
are of the following order (Kp) 304SS (Kp) 316SS > (Kp) low alloy steel .
The scale-removal-rate constants Kr by mass transfer corrosion are of the
following order (Kr) inconel > (Kr) 316SS > (Kr) 304SS . The weight loss
increases with increasing Ni content in the steel alloys.