Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : Pack cementation


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.

Taguchi Approach to Optimize Pack Aluminization Parameters in Carbon Steel Using MINITAB13

Abbas Khammas Hussein

Engineering and Technology Journal, 2009, Volume 27, Issue 11, Pages 2259-2272

Pack aluminization has been rapidly developed and widely used in many fields
due to its superior properties of coating. Surface is the only part of the component
which has to coexist with external environment. Majority of engineering failures
originate from the surfaces and components degrade in service leading to failures such
as fatigue, wear, corrosion and oxidation. The present study deals with the surface
modification of steel base through diffusion of aluminium by aluminium pack
cementation for improving wear and corrosion resistance. The material chosen for
study is medium carbon steel. Effect of varying weight percentage (wt.%) of halide
activator (NH4Cl) at different diffusion temperatures and times on the microstructure
and microhardness of aluminized specimens was studied. Taguchi robust design
technique using MINITAB13 was used to rank several factors that may affect the
microhardness and microstructure in order to formulate the optimum conditions. The
Taguchi orthogonal array L9 (33) was used for experimental design with three level of
consideration for each factor. The respone (Microhardness) was analyzed based on the
Taguchi’s signal-to-noise ratio. The use of 4%wt. of (NH4Cl) at 5hr and diffusion
temperature of 700oC seems to be the optimum condition, where the surface hardness
could be increased to 1000Hv when aluminized. X-Ray diffraction studies have been
confirmed the presence of aluminides in the surface layer, which could be instrumental
in the significant increase in the surface hardness.

Oxidation Properties of Steel-T22 Alloy Coated by Simultaneous Ge-Doped 699 Chromizing-Siliconizing Process

Ahmed A. Moosa

Engineering and Technology Journal, 2008, Volume 26, Issue 6, Pages 699-709

Diffusion coating was carried out at 1050 oC for 6 h under argon atmosphere by
simultaneous Ge-doped chromizing-siliconizing process on low alloy steel type-T22.
Cyclic oxidation tests were conducted for the uncoated and for the chromizing –
Siliconizing coated steel-T22 alloy at 800 oC . For the Ge-dopded chromizingsiliconizing
coated steel, the cyclic oxidation was carried out in the temperature range
600-800 oC in air for 100 h at 5 h cycle. The results showed that the oxidation kinetics
for uncoated steel-T22 alloy in air at 800 oC follow a breakaway oxidation and the
phases present are FeO (Wustite), Fe3O4 (Magnetite) and Fe2O3 (Haematite).
The oxidation kinetics for chromizing –Siliconizing coated system in air at 800 oC
was found to be parabolic. Oxide phases that formed on coated system are SiO2 and
Cr2O3. The oxidation kinetics Ge-doped chromizing –Siliconizing coated system in air in
the temperature range 600-800 oC was found to be parabolic .Oxide phases that formed
on coated system are SiO2 and Cr2O3. The Ge addition improves the oxidation resistance
of low alloy steel.