Effect of the La2O3 sol-gel coating on the alumina scale adherence on a model Fe-20Cr-5Al alloy at 1100 degrees C

摘要

The effect of lanthanum sol-gel coatings was studied in order to improve the alumina scale adherence during the model Fe-20Cr-5Al alloy oxidation, at 1100 degrees C, in air. Various sol-gel coating procedures were applied. Argon annealing of the lanthanum sol-gel coating was tested at temperatures ranging between 600 and 1000 degrees C. The coating crystallographic nature was characterized by X-ray diffraction (XRD) depending on the annealing temperature. The oxidation process has been examined at 1100 degrees C by in situ XRD on blank Fe-20Cr5Al, sol-gel coated and argon-annealed specimens. This study shows that the coating argon annealing at 1000 degrees C leads to the preferential formation of LaAlO3 instead of La2O3. This coating procedure leads to an alumina scale formation showing the best adherence under thermal cycling conditions at 1100 degrees C.