Oxidation behaviour of V2AlC MAX phase coatings

We report on the oxidation behaviour of V2AlC coatings up to 800 degrees C, in air. The coatings were deposited at 580 degrees C using magnetron sputtering from a powder metallurgical composite V2AlC target and were subsequently oxidised for 5, 15 and 30 min. The microstructural evolution of the samples was investigated, and X-ray diffraction patterns were collected to track the formation of oxides. The first indications of oxidation appear after just 15 min at 500 degrees C, as V-based oxides grew on the surface of the coatings. Later, the presence of mostly V-based oxides and ternary (V, Al)-oxides was observed starting after 5 min at 600 degrees C. Further analyses confirmed outward diffusion of V and inward diffusion of O, while Al tends to sublimate. alpha-A12O3 was only indexed after 5 min at 800 degrees C. Ex-situ electrical resistivity measurements allowed tracking the oxidation progress of the V2AlC coating.