Infiltration of Open Porous Cellular Iron with α-Al2O3

Open porous cellular iron may be used as structural material but also in filters and heat exchangers due to its large specific surface area, low density, and good thermal conductivity. Currently, the low oxidation resistance of iron limits its use. One way to enhance the oxidation resistance is to deposit a protective alpha-Al2O3 coating onto the cellular iron surface using chemical vapour infiltration. Here, we investigate the influence of deposition temperature on the alpha-Al2O3 coating thickness homogeneity. Furthermore, the oxidation resistance of the infiltrated cellular iron is studied by thermogravimetric analysis. X-ray diffraction results show that phase-pure alpha-Al2O3 coatings grow at 950 similar to 1100 degrees C. Homogeneous coating thickness is favoured at infiltration temperatures below 1000 degrees C, which is a prerequisite for efficient oxidation protection. Based on the thermogravimetric analysis at 600 degrees C, the parabolic rate constant of the as received cellular iron is 56% larger than its three hour-infiltrated counterpart, indicating an improved oxidation resistance due to the protective filrn. In-line processing integrating annealing on green cellular iron sample and TiN infiltration treatment steps in one process was successfully carried out.