Author : A. Moosa, Ahmed
Oxidation Properties of Steel-T22 Alloy Coated by Simultaneous Ge-Doped 699 Chromizing-Siliconizing Process
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.