Samples of alloy 800 H (UNS N08810) and alloy 617 (UNS N06617) were oxidized in a simulated process gas atmosphere. The principal elements of the gaseous environment were 50 % H2O, 35% H2 and 5% of CO2, CO, and CH4, respectively and a total pressure of 140 kPa. This gas in a state of thermodynamic equilibrium establishes oxygen partial pressures ranging from 3.0 x 10-17 kPa, at 800 °C to 3.2 x 10-14 kPa at 950 °C. The exposure time was from 600 to 5000 hours. After the exposure the alloy surfaces showed compact oxide ayers. On alloy N08810 a double oxide layer was built. A first layer was identified as the spinel phase, Mn(1+x)Cr2(1-x)TixO4. The second one is the corundum type phase, Cr2-yTiyO3 On alloy N06617, lack of manganese produces the growth of a single layer, which was also identified as the phase Cr2-yTiyO3

Subject
Oxide formation, Oxide layers, Partial pressures, Titanium oxide, Manganese, Oxide scales, Chromium oxide, Oxide surfaces, Titanium, Elements, Titanium alloys, Alloys, Oxidation
Keywords:
low oxidation potential, double layer, titanium doped chromium oxide, chromium- manganese-titanium spinel
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1996
Association for Materials Protection and Performance (AMPP)
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