High-temperature corrosion properties of chromia- and alumina-forming alloys
Doktorsavhandling, 2022
In environments with high concentrations of oxygen and water, chromia-forming Ni-base alloys suffered extensive volatilization of chromium-oxy-hydroxide. The resulting chromium depletion of the alloy triggered nickel oxidation which, in turn, caused a NiO layer to form on top of the chromia scale. The NiO ‘cap-layer’ reduced chromium evaporation rate, resulting in a secondary chromia scale being established at the oxide/metal interface. Cr-containing alloys forming alumina scales, showed a very limited evaporation rate of chromium-oxy-hydroxide. In the nitriding environment, the ability of the scale to prevent nitridation was studied. Gravimetric and GD-OES analyses showed that the presence of a chromia scale decreased the nitridation by 50-95%. A beneficial effect was observed for a two-layered scale that contained both chromia and silica, as this gave a nitridation reduction at the higher limit of the interval, i.e., 83-95%. Furthermore, the study showed that alumina scales without macro defects completely block the ingress of nitrogen.
High-temperature corrosion
Alumina scale
Chromia scale
Cr-evaporation
Nitridation
Oxidation
Författare
Tommy Sand
Chalmers, Kemi och kemiteknik, Energi och material
T. Sand, A. Rajagopal, M. Sattari, S. Bigdeli, M. Hättestrand, J.E. Svensson, M. Halvarsson, L.G. Johansson. Nitridation of austenitic alloys at 1100 °C
A Comparison of the Oxidation and Nitridation Properties of Selected Chromia- and Alumina-Forming Alloys at 800 degrees C
Oxidation of Metals,;Vol. In Press(2022)
Artikel i vetenskaplig tidskrift
Ämneskategorier
Metallurgi och metalliska material
Korrosionsteknik
Styrkeområden
Materialvetenskap
ISBN
978-91-7905-662-9
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5128
Utgivare
Chalmers
KC, Kemigården 4
Opponent: Mathias Galetz, Dechema, Germany