Effect of Si additions on the Al2O3 grain refinement upon oxidation of Cr2AlC MAX phase

The effect of Si additions on the oxidation behavior of Cr2AlC based coatings is investigated. Oxidation experiment was performed at 1120 °C in air for 4 h for Cr2AlC and Cr2Al1−xSixC (0 < x ≤ 0.06) coatings. The crystal structure, microstructure and chemical composition of the as-deposited as well as oxidized coatings have been investigated. Alloying Cr2AlC with up to 0.7 at.% Si causes an increase in Al2O3 scale thickness by up to 40 ± 17%. Electron microscopy and atom probe tomography data support the notion that the here reported Si concentration induced 40% increase in Al2O3 layer thickness (during oxidation at 1120 °C for 4 h) is enabled by the Si concentration induced, and hence concomitant, increase in nucleation density of Al2O3.