Oxidation behaviour of the MAX-phases Ti2AlC and (Ti, Nb)2AlC at elevated temperatures with and without fluorine treatment. Issue 15 (December 2019) - Donchev, Alexander
Abstract: MAX-phase materials have shown great potential for different technical applications due to their mechanical properties. If the main group element is aluminium their excellent oxidation resistance also makes them attractive for several high temperature applications. As an example the thermodynamically stable MAX-phase Ti2 AlC forms a thin, protective alumina layer in oxidising atmospheres at elevated temperatures. This alumina layer is formed due to the high Al activity within the material and prevents further attack by the environment. However, high temperature oxidation tests at 900 °C in air of "technical" Ti2 AlC which is not pure single-phase Ti2 AlC led to the formation of a non-continuous alumina scale which is intersected by a mixed TiO2 /Al2 O3 scale. Furthermore, internal oxidation was observed. This "technical" material consists of two phases namely Ti2 AlC plus γ-TiAl due to the manufacturing route. Such γ-TiAl-grains are preferentially oxidised. This type of internal attack can be suppressed by a preceding fluorine treatment.